  We present a theory for spin-polarized scanning tunneling microscopy (SP-STM)
of a Kondo impurity on an unpolarized metallic substrate. The spin polarization
of the SP-STM breaks the spin symmetry of the Kondo system, similar to an
applied magnetic field, leading to a splitting of the Abrikosov-Suhl-Kondo
resonance. The amount of splitting is controlled by the strength of the
coupling between the impurity and the SP-STM tip and also the overall spin
polarization of the SP-STM.
