We present a theoretical study of electronic properties of the Pd-Si(111) interface in the early stages of interaction. Three models are considered: a chemisorbed Pd layer on Si, an epitaxial Pd2Si layer on Si, and a near-surface Si layer containing interstitial Pd atoms. By comparing the results of our calculations with the spectroscopic data, we find that the model of mixing interstitial Pd atoms in Si is the most appropriate one. This suggests an interpretation of the interfacial reaction in terms of a precursor state of formation of Pd silicide. © 1984 The American Physical Society.