Cobalt and copper were elect rodeposited on n-type. 100-oriented, p rite slices. The occurrence of a favorable chemical interaction with the pyrite interface is marked by the appearance of pronounced prebulk deposition (PBD) features in the case of Co. This metal leads to the formation of highly ohmic metallic contact, while deposition of Cu provides a significant Schottky barrier. The effects of electrodeposited Co and Cu can be explained by the formation of the pyrite-type Compounds CoS2 and CuS2, at the interface, which are n- and p-type metallic compounds. respectively. When time for diffusion is allowed, mixed CoxFe1-xS2 and CuxFe1-xS2 phases are also to be expected as learned from XPS experiments on (electron beam evaporated) Co/(MOCVD) pyrite layers. A model is proposed which links the electronic properties of these disulfides with their solid state chemical behavior in the pyrite structure and with their ability to form PBD layers (Co).