Fermi Surface of the Half Heusler Compounds Ce$_{1-x}$La$_{x}$BiPt

We report on the Fermi surface in the correlated half-Heusler compound Ce$_{1-x}$La$_{x}$BiPt. In CeBiPt we find a field-induced change of the electronic band structure as discovered by electrical-transport measurements in pulsed magnetic fields. For magnetic fields above $\sim$25~T, the charge-carrier concentration determined from Hall-effect measurements increases nearly 30\%, whereas the Shubnikov--de Haas (SdH) signal disappears at the same field. In the non-$4f$ compound LaBiPt the Fermi surface remains unaffected, suggesting that these features are intimately related to the Ce 4$f$ electrons. Electronic band-structure calculations point to a $4f$-polarization-induced change of the Fermi-surface topology. In order to test this hypothesis, we have measured the (SdH) signal in a Ce$_{0.95}$La$_{0.05}$BiPt sample with a low La concentration.