The reaction of very thin (0.5–20 nm) layers of Ni with amorphous Si has been investigated by means of transmission electron microscopy and diffraction. The experiment, which is directly parallel to a previous study of similar samples prepared with Pd and Pt, has led to different observations. With Ni it is found that an amorphous Ni‐Si solution is formed first, and that silicide formation, at temperatures which decrease with the amount of deposited Ni, results from the crystallization of that amorphous phase. With Pt and Pd microcrystalline silicides had been observed immediately.