This is one you may or may not have heard
http://www.youtube.com/watch?v=_BQrjb7-d_MThe rest of their album "A Book Like This" is really fucking good. Both have pretty distinctive voices and share vocal duties from track to track. I didn't like "The Beast" at first, I found it a bit silly. But it's catchy enough. They have better songs though, "Here We Go Again" is achingly beautiful (
http://www.youtube.com/watch?v=FXs-7EfD13w) as is "Bella".
If you like any kind of folk-pop with boy-girl harmonies and harmonica's and stuff you'll love them.