We report the first synthesis of CoSi in the CsCl structure, as an epitaxial film on Si(111). Experimentally and theoretically we find that the lower stability of this phase, relative to that of FeSi with the same structure, can be understood only by taking into account the energy contribution for the interface bonding, in addition to the elastic energy.

• Received 9 August 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.1163