  Below the Kondo temperature $T_{\rm K}$ electron spin resonance (ESR) usually
is not observable from the Kondo-ion itself because the characteristic spin
fluctuation energy results in a huge width of the ESR line. The heavy fermion
metal YbRh$_{2}$Si$_{2}$ seems to be an exceptional case where definite ESR
spectra show characteristic properties of the Kondo-ion Yb$^{3+}$ well
\textit{below} $T_{\rm K}$. We found that the spin dynamics of
YbRh$_{2}$Si$_{2}$, as determined by its ESR relaxation, is spatially
characterized by an anisotropy of the zero temperature residual relaxation
only.
