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The high-temperature coercivity of mechanically alloyed and subsequently annealed RCo5 (R=Sm and Y) is studied. The annealed materials have the hexagonal CaCu5 structure with 2 : 17 (or 1 : 7) regions as a minor phase. High-temperature magnetic measurements showthat the coercivities of materials decrease with increasing temperature fromroom-temperature to 873 K, but that the temperature coefficient of the coercivity of YCo5 is much smaller than that of SmCo5. This behavior is explained in terms of the intrinsic temperature variation of the magnetocrystalline anisotropy.