A copper alloy having the following composition (in % by weight): in each case 0.05 to 0.5% of at least three elements selected from the group consisting of Ag, Ni, Zn, Sn and Al, remainder Cu and unavoidable impurities, optionally 0.01 to 0.2% of one or more elements selected from the group consisting of Mg, Ti, Zr, B, P, As, Sb. Also, a current-carrying structural part made of a copper alloy and a cage rotor having multiple conductor bars and two short-circuiting rings, which are cast in one piece from a copper alloy.