Polycrystalline Pd2Si is found to reorder on top of epitaxial Pd2Si during silicide growth. The interface between polycrystalline Pd2Si and epitaxial Pd2Si is, thus, not immobile with respect to the silicide lattice during silicide formation and it is, therefore, not possible to use this interface as a structural marker in order to monitor diffusion in epitaxial Pd2Si. The use of Ti as an inert marker has shown that Si is the dominant diffusing species in epitaxial Pd2Si during silicide formation.