Sm(Co0.08Cu0.13)zalloys were prepared with . Homogenization heat-treatment yielded single phase 2-17 material for . For some of the Co was substituted by Fe. The alloys remained single phase for up to 15 % Co substituted. With further increasing Fe content a Co-Fe phase appears accompanied by a strong decrease of the hard magnetic properties. The compounds were hard magnetic in bulk form with ideal rectangular hysteresis loops. The coercivity could be increased by a factor > 2 with a low temperature heat-treatment. BRvalues > 11 kG together withIHcvalues of about 4 kOe were achieved on single crystal samples. The coercivity mechanism in these materials is pinning of Bloch walls.