  We argue that because of valence-fluctuation caused dynamical changes
(fluctuations) of impurity energies in an impurity band of valence fluctuating
semiconductors both occupied and unoccupied sites can be found in the impurity
band above as well as below the Fermi level even in the ground state. As a
consequence, the ground state energy distribution function of the subsystem of
localized charge carriers for valence fluctuating semiconductors is
qualitatively different than one for conventional semiconductors at T = 0 K,
what sheds new light on interpretation of experimental results of valence
fluctuating semiconductors, e.g. SmB6 and YbB12, at lowest temperatures.
