The variation of coercive force as a function of annealing temperature is reported for some compacts of Co5Sm and Co5Pr alloys with the compositions of 63∼64 wt&percent; Co‐Sm and 60∼64 wt&percent; Co‐Pr, respectively. For the magnets made of these alloys, the curves of intrinsic coercive force against annealing temperature have two peaks; one at around 1080 °C and the other at 1190 °C in the Co‐Sm sintered magnets. The curves of coercive force in sintered Pr‐Co alloys have also two peaks; one near 1040 °C and the other near 1125 °C. This behavior can be correlated with the peritectic temperatures in the Co‐Sm and Co‐Pr phase diagrams. It is interpreted in terms of a model which assumes the existence of the pinning sites for the domain walls and their concentration at boundaries between the precipitates and grains of Co5Rduring the sintering. These precipitates are thought to consist of otherR‐Co compounds with lower melting points thanRCo5.