A superconductive element containing Nb3Sn, 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 αcore<17*10−6K−1, preferably αcore≦8*10−6 K−1, said metallic material having at RT a yield strength Rp0.2>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 Tc and a high critical magnetic filed strength Bc2, and is mechanically stable enough for commercial applications such as
magnet coils.