  We report on a topological insulating state in a heavy-fermion system away
from half-filling, which is hidden within a ferromagnetic metallic phase. In
this phase, the cooperation of the RKKY interaction and the Kondo effect,
together with the spin-orbit coupling, induces a spin-selective gap, bringing
about topologically non-trivial properties. This topological phase is robust
against a change in the chemical potential in a much wider range than the gap
size. We analyze these remarkable properties by using dynamical mean field
theory and the numerical renormalization group. Its topological properties
support a gapless chiral edge mode, which exhibits a non-Tomonaga-Luttinger
liquid behavior due to the coupling with bulk ferromagnetic spin fluctuations.
We also propose that the effects of the spin fluctuations on the edge mode can
be detected via the NMR relaxation time measurement.
