ANDREEV REFLECTION ON THE AG-BAPB1-XBIXO3 MICROCONSTRICTION - TEMPERATURE AND MAGNETIC-FIELD DEPENDENCE

The point-contact spectroscopy has been performed on the normal metal- superconductor microconstriction Ag-BaPb1-xBixO3. The conductance curv es of our junctions reveal almost ideal Andreev reflection behavior de scribed by the Blonder-Tinkham-Klapwijk theory, with the in-gap conduc tance twice higher than the conductance at higher voltages. We studied the effect of the temperature and magnetic field on the Andreev refle ction. The temperature dependence of the energy gap (determined from t he BTK theory) follows the BCS prediction. The value of the reduced ga p, yields a weak coupling strength in BaPb1-xBxO3. From magnetic measu rements up to 10 Tesla the temperature dependence of the upper critica l field H-c2 has been determined and found to follow the Werthamer-Hel fand-Hohenberg prediction.