Sprite sheet sprites into a material

I created a Coin which contains two materials: one for the face, and one for the everything-else.

I have a .psd Sprite Sheet, and I've split it up into sprites in Unity. The sprite sheet has copies of the coin face with other numbers, so that I can make coins of different values.

Only problem: I dont know how to make a sprite into a material. Any suggestions?

Thanks in advance.