Anomalous behavior of superconducting-normal mesoscopic structures near T-c

We observe a maximum in the conductance of Al/n-GaAs junctions at temperatu res 20 mK lower than the superconducting transition temperature (T-c). This is the first observation of a peak in the conductance near the superconduc ting transition in superconducting-normal (S/N) junctions. To accommodate t his effect we calculate the full temperature dependence of the conductance of these structures, invoking quasiclassical Green's functions in the diffu sive limit. In addition to the well-known low-temperature peak at temperatu res on the order of the Thouless energy, we find a maximum near T-c. This p eak has the same origin as the subgap conductance observed in S/N junctions at low temperatures.