The growth of ultra-thin, lattice matched, Cr0.7Mo0.3 films on an MgO substrate, in a dc magnetron discharge, was investigated by in situ measurements in order to determine the minimum thickness of a continuous layer. The thickness dependence of the resistivity shows a coalescence thickness of less than two monolayers indicating layer by layer growth of the films. We compare the resistivity of the films to a combination of the Fuchs- Sondheimer and the Mayadas-Shatzkes models, assuming a thickness dependence of grain size. The model indicates that grain size increases with increasing growth temperature. (c) 2005 Elsevier B.V. All rights reserved.