In situ resistivity measurements together with MeV 4He + backscattering, x-ray diffraction, barrier height measurements, and Auger electron spectroscopy combined with Ar sputtering have been used to investigate the interaction of silicon with alloys of rare-earth and near-noble metals with annealing at temperatures up to 650°C. Alloys of Pd-Er with three different compositions have been prepared by dual electron-gun coevaporation on both n- and p-type silicon and Pd/Er bilayers have been deposited on SiO2. The results show that as-deposited these alloys are amorphous and the initial stages of the reaction with silicon upon annealing is controlled by the metal-metal interaction as well as the metal-silicon interaction. The Er-rich alloy (Pd15Er8 5) segregates Er to the silicon interface and forms Pd 2Er5. The segregated Er reacts with silicon producing ErSi2. For the Pd-rich alloy (Pd65Er 35) the excess Pd is segregated at the silicon surface forming Pd2Si. The near 50-50 alloy forms PdEr and a slightly higher temperature is necessary to promote the reaction with silicon to form the silicide of the excess component.