We show how analysis of the stacking sequences at CoSi2/Si interfaces formed by 100 kV Co+implantation into Si (001) or (111) predicts the formation of partial dislocations or stacking faults at precipitate corners. The presence and nature of the stacking fault can uniquely identify the bonding coordination at the CoSi2/Si(111) interface. Consideration of the interfacial structure for twinned (B) and untwinned (A) {111} interfaces helps explain the competitive nucleation and growth ofAvsBprecipitates.