Yesterday on NPR was a report on the liberation of Mauthausen. It can be found here:
http://www.npr.org/templates/story/story.php?storyId=4632393
Features interviews with Edgar Edelsack, a member of the 11th Armored as well as Martin Weiss, a former detainee from Mauthausen. Although they did not identify the specific unit of the 11th that Edgar Edelsack was in.

Thanks!