Permanent magnets made from SmCo5 exhibit negative reversible change in magnetization with increasing temperature, typically of the order of 0.04% per deg. C. between -100 and +200 C. It is desirable to improve this property by suitable substitutions. In the present study, a systematic examination of the preparation, structural and magnetic characterization of SmxR1-xCo5 (R=Tb, Dy and Er) has been undertaken. The ternaries were prepared by induction melting of the metals of proper stoichiometries. Magnetic studies were performed between 4.2 and 1000 K in applied fields up to 20 kOe. The results indicate that the best temperature compensation is achieved in the ternary SmxDy1-xCo5. Saturation magnetization and Curie temperatures are also reported.