In this investigation, the crystalline structure of a nanometric CoSi2 layer, formed in heat treated Co/WxTa(1-x)/Si(100) systems, has been studied by XRD analysis. Careful measurements of the diffraction intensities revealed that temporary formation of a metastable diamond cubic structure of CoSi2 phase, rather than its usual CaF2 structure, was occurred. It has been shown that formation of this metastable structure depends on the kind of the applied interlayer in addition to the annealing temperature. Among the studied systems with x = 0, 0.25, 0.5, 0.75 and 1, the second and the last systems resulted in growing a (100) single-texture CoSi2 layer with the preferred usual CaF2 structure, a strained lattice parameter, and the best thermal stability (900-1000 degrees C). (c) 2006 Elsevier B.V. All rights reserved.