The Co-rich region (0 to 30 at.% Sm) of the Co-Sm phase diagram was reevalu
ated. The homogeneity range of Co5Sm was redetermined with optical metallog
raphy, Curie temperature measurements, and lattice parameters data. Some co
mments on the phases Co7Sm2, Co19Sm5, Co5Sm, and Co17Sm2 are presented. The
homogeneity range of other Co5RE and Co17RE2 (RE = rare-earth) compounds i
s discussed.