  A yet unknown surface reconstruction of V3Si(001), which is most likely
induced by carbon, is used to investigate the quasi-particle energy gap at the
atomic scale by a cryogenic scanning tunneling microscope. The width of the gap
was virtually not altered at and close to carbon impurities, nor did it change
at different sites of the reconstructed surface lattice. A remarkable
modification of the spectroscopic signature of the gap was induced, however,
upon moving the tip of the microscope into controlled contact with the
superconductor. Spectroscopy of the resulting normal-metal -- superconductor
junction indicated the presence of Andreev reflections.
