Angular relation and energy dependence of Andreev reflection

Andreev reflection at an interface between an Ag single crystal and a Pb film is studied by an electron-focusing experiment. Quasiparticles are observed to be reflected within a cone with an angle {}10^-4 rad centered about the incident direction. The energy dependence of Andreev reflection is found to be consistent with theory. In spite of the nonideal circumstances during the Pb deposition, the probability for Andreev reflection approaches that of a perfect interface.