Compound having a high conductivity for electrons, which is of the type ABCO(x-δ)Hal(y-ζ) with a potassium nickel fluorite structure, where x+y=4, and δ and ζ lie between −0.7 and +0.7, and wherein A comprises at least one metal selected from the group consisting of Na, K, Rb, Ca, Ba, La, Pr, Sr, Ce, Nb, Pb, Nd, Sm and Gd, and wherein B comprises at least one metal selected from the same group, and wherein C comprises at least one metal selected from the group consisting of Cu, Mg, Ti, V, Cr, Mn, Fe, Co, Nb, Mo, W and Zr and/or a metal selected from the group consisting of Pt, Ru, Ir, Rh, Pd and Ni, wherein A and B are not identical and wherein A and C are not both Nb and wherein Hal comprises at least one halogen atom selected from the group consisting of F, Cl, Br and I.