Giant Sommerfeld coefficient in the heavy-fermion YbBiPt

It has been derived that the Sommerfeld coefficient $\gamma$ as large as 25 J/K${}^2$mol can be theoretically accounted for provided the charge f-electron fluctuations are substantially suppressed. This result enables the understanding of the heavy-fermion YbBiPt ($\gamma$ =8 J/K${}^2$mol) as the spin fluctuator and should stimulate the experimental specific-heat research at low temperatures.