The 'Twilight Saga' hunk – who has been single since splitting from Kristen Stewart earlier this year – has been close to Sarah since meeting on the set of 'Cosmopolis' in 2011 and they have been spending even more time together after reuniting while working on their latest movie.
A source told the US edition of OK! Magazine: “There’s a real spark between them. And they’ve already been spending time together when filming ends for the day.
“They have become very close. When there’s a break in filming, they’ll often sit on their own and chat.
Sarah’s really into the arts and literature, which Rob loves. And they even talk about English soccer together because she watches games on TV. They have a lot in common.”
Robert, 27, is thought to be smitten by Sarah because she doesn't fawn all over him.
The insider added: “It’s sexual tension and she seems to be wooing him by treating him mean … Rob’s having a lot of fun with Sarah. She’s like a breath of fresh air after Kristen and they look like a really cute couple together.”