The signature of subsurface Kondo impurities in the local tunnel current.

The conductance of a tunnel point contact in a scanning tunneling microscope-like geometry having a single defect placed below the surface is investigated theoretically. The effect of multiple electron scattering by the defect after reflections by the metal surface is taken into account. In the approximation of s-wave scattering the dependence of the conductance on the applied voltage and the position of the defect is obtained.