A solid-state wetting technique has been used to investigate the interface between solid Cu and alpha-SiC at high temperatures. An intermediate phase is found to form as an interfacial reaction product between Cu and SiC at high temperature, and to thicken upon further heating at 1123 K. The interfacial phase has an approximate composition of Cu-19 at %Si-5 at %C and displays an f.c.c. structure. Such a phase is not present in the published Cu-Si phase diagram, and forms under conditions which cannot be explained from that phase diagram. It is postulated that this phase represents a previously unreported silicide of Cu which may be stabilized by the presence of C in solution.