Tunneling in binary alloys

The effect of the phase composition of alloys on superconducting tunneling was studied experimentally in the Pb--Bi system. The application of pressure up to 14 kbar together with stepwise annealing up to 370/sup 0/K followed by quenching to 4.2/sup 0/K enabled us to show that for Pb alloys with 10--63 at.% Bi the multiphase nature of the alloys is directly reflected in the tunneling characteristics. For alloys beyond the eutectic composition (>60%Bi) quenched from above 100/sup 0/C, we observed characteristics typical of pure metals, which we associate with a range of existence of the single-phase composition which is wider than that in the accepted phase diagram.