@dkendig said:
.mat is a 3d studio max format. You want a .vrmat or .vismat format. There are quite a few available for download on the Chaos Group website, as well as V-Ray Express for SketchUp, which will give you a nice library of V-Ray materials and lighting/studio scenes to import and play with. Not sure if you will have full access to these resources until after you purchase a license, but either way, you need to use a .vrmat or .vismat.
Thanks for the speedy response! Will give it a try.