[en] This paper describes a superconductor having a core. It comprises: alkaline earth metal copper oxide based material having superconductivity capability, enclosed by a contacting metallic sheath, the sheath comprising a layer of Ag-Pd alloy, containing interdispersed, discrete particles of a metal selected from the group consisting of W, Mo, Ni, and mixtures thereof, where the particles have diameters from 0.05 micrometer to 75 micrometers and constitute from 5 weight % to 45 weight % of the total alloy-particle weight