Sierra Deaton

For the Four Chair Challenge, Alex & Sierra took on the John Travolta/Olivia Newton-John classic "You're The One That I Want" from the 1978 musical film Grease.

The judges praised the duo for putting their own twist on the song.

Kelly Rowland and Paulina Rubio felt the performance was "nice" and said they had "sexiness" to them, while Demi Lovato told them they were one of their favorite acts but questioned the future and their relationship.

Despite this controversy, the duo made it through to the live shows.

For the first live show, Alex And Sierra earned a spot in the top 12 after performing a stripped-down version of the Robin Thicke hit "Blurred Lines".

Kelly Rowland wished it had been a bit sexier and thought it got corny at times, something Simon Cowell disagreed with, praising Alex & Sierra's performance, calling it "original" and "unique".

For Motown Night, they took on "I Heard It Through The Grapevine" by Marvin Gaye.

Paulina felt it was "natural," while Demi said it felt "organic" as well as very "hot" and "sexy".

On the re-vote show, which happened due to a graphics error that nullified the votes, Alex & Sierra sang "Give Me Love" by Ed Sheeran; Cowell afterward said that the performance was "immaculate... ragged and raw."

For '80s Night, the couple took on the Robert Palmer classic "Addicted to Love".

The performance earned them negative reviews; Kelly wanted them together more, Paulina called them "Bohemian" and "vintage", Demi felt that Sierra looked uncomfortable in her shoes and wanted the performance more organic, and their mentor Simon expressed disappointment over how the performance went by saying that they lost the melody in the beginning and "it wasn't as good as it should have been."

For British Invasion night, Alex & Sierra took on the One Direction hit "Best Song Ever".

Demi Lovato called it their best performance and said they planned to download the song on iTunes.

However, Sierra's vocals were criticized for not being as strong as Alex's. Their version charted on the top 40 of the US iTunes, the first act to do so that season.

For Big Band night, Alex & Sierra performed Taylor Swift's hit "I Knew You Were Trouble".

Demi said that they didn't like the arrangement at first, but Alex & Sierra made them like it by the end.

Simon said that their arrangement was clever and cool and not obvious, and also praised Sierra: "You just shut up the witches of Eastwick here because that was a great, great vocal performance."

They later faced off against the others in a group performance of "Cry Me A River", in which they received praise from Kelly, who said they "soared".

For Divas/Unplugged night, the couple sang two songs.

Their "Diva" song was "Say My Name" by Destiny's Child.

The song earned them praise from Kelly, who said she adored the new sassy side of Sierra.

Their "Unplugged" song, "Say Something" by A Great Big World and Christina Aguilera (thought by many as their best X Factor performance) earned them praise by the judges; Kelly said she felt like she was watching an awards show, Demi felt that the performance was "magical", Paulina was impressed with Sierra's talent with the piano, and Simon stated that this was not only their best performance of the night but of the season.

Their version of the song hit number one on the US iTunes charts, which was the first time that a song from the US X Factor reached the top position.

For the semi-final, the public chose "Little Talks" by Of Monsters and Men, which pleased the judges; Kelly said they nailed it, Demi felt they were looking at the winners, Paulina said that they kept coming back stronger and suggested that there was a huge gap in the industry for them, and Simon said they were not just performing - they were making records each week.

They faced Carlito Olivero in The Duet Duels singing "Falling Slowly" with the judges feeling that while Carlito and Alex did well, Sierra stole the song.

but it was their performance of "Gravity" by Sara Bareilles that earned high remarks.

The judges felt that Sierra had blossomed during the competition, Alex's vocals were "fricking crazy" and their performance was "perfect."

Like "Say Something" before it, the couple's version of "Gravity" hit number 1 on iTunes.

For the finals, Alex & Sierra sang three songs.

They did their "save me" song from the re-vote show as their "song to win", "Give Me Love" by Ed Sheeran.

They also sang "Bleeding Love" with Leona Lewis, and their "song of the season" was "Say Something".

The "Bleeding Love" performance received a bit of a mixed response mainly from Demi Lovato, who said that it wasn't their best performance, but the other two songs received praise.

In the finale result show, Alex & Sierra performed "All I Want For Christmas Is You".

Alex & Sierra were an American duo consisting of Alex Kinsey (born September 8, 1991) and Sierra Deaton (born February 11, 1991), who won the third and final season of The X Factor US.

They were mentored by Simon Cowell.

Their debut album It's About Us was released on October 7, 2014, on Columbia Records.

Their EP As Seen on TV was released on September 30, 2016.

On September 1, 2017, Alex & Sierra announced to the media that they had broken up more than a year earlier, and would no longer continue to make music together, but would branch out into their own solo careers.

Alex & Sierra auditioned in New Orleans, Louisiana, making it to the next round after wowing the judges with a sultry version of Britney Spears' "Toxic".

They continued on to the top 40 and received Simon Cowell as their mentor.