A superconductive element containing Nb.sub.3Sn, in particular a multifilament wire, comprising at least one superconductive filament (8) which is obtained by a solid state diffusion reaction from a preliminary filament structure (1), said preliminary filament structure (1) containing an elongated hollow pipe (2) having an inner surface (3) and an outer surface (4), wherein said hollow pipe (2) consists of Nb or an Nb alloy, in particular NbTa, wherein the outer surface (4) is in close contact with a surrounding bronze matrix (5) containing Cu and Sn, and wherein the inner surface (3) is in close contact with an inner bronze matrix (5) also containing Cu and Sn, is characterized in that the inner bronze matrix (5) of the preliminary filament structure (1) encloses in its central region an elongated core (6) consisting of a metallic material, said metallic material having at room temperature (=RT) a thermal expansion coefficient .alpha..sub.core<17*10.sup.-6K.sup.-1, preferably .alpha..sub.core.ltoreq.8*10.sup.-6 K.sup.-1, said metallic material having at RT a yield strength R.sub.p0,2>300 MPa, said metallic material having at RT an elongation at rupture A>20%, and wherein the metallic material of the core (6) is chemically inert with respect to the material of the inner bronze matrix (5) up to a reaction temperature T of the solid state diffusion reaction. This element has improved superconductive properties in a large volume fraction of its superconductive filaments, in particular a high critical temperature T.sub.c and a high critical magnetic filed strength B.sub.c2, and is mechanically stable enough for commercial applications such as magnet coils.