  Electron scattering off an Anderson impurity immersed in the bulk of a 3D
topological insulator is studied in the strong coupling regime, where the
temperature $T$ is lower than the Kondo temperature $T_K$. The system displays
either a self-screened Kondo effect, or a Kondo effect with SO(3) or SO(4)
dynamical symmetries. Low temperature Kondo scattering for systems with SO(3)
symmetry displays the behavior of a singular Fermi liquid, an elusive property
that so far has been observed only in tunneling experiments. This is
demonstrated through the singular behavior as $T \to 0$ of the specific heat,
magnetic susceptibility and impurity resistivity, that are calculated using
well known (slightly adapted) conformal field theory techniques. Quite
generally, the low temperature dependence of some of these observables displays
a remarkable distinction between the SO(n=3,4) Kondo effect, compared with the
standard SU(2) one.
