"Universal" degradation ofTcinNb3Sn: No effect of Coulomb interaction

On the basis of electron tunneling experiments and numerical $T_c$ calculations, we show that the "universal" degradation of $T_c$ in samples of composition ${\mathrm{Nb}}_x{\mathrm{Sn}}_{1-x} (0.75\mathrm{}<~x<~0.81)$ cannot be explained by a disorder-induced increase in the Coulomb repulsion parameter ${\mu }^{*}$.