An alloy made of heat treated material represented by Gd₅(Si_xGe_1−x)₄ where 0.47≦x≦0.56 that exhibits a magnetic entropy change (−ΔS_m) of at least 16 J/kg K, a magnetostriction of at least 2000 parts per million, and a magnetoresistance of at least 5 percent at a temperature of about 300K and below, and method of heat treating the material between 800 to 1600 degrees C. for a time to this end.