Fermi Surface of the Half Heusler Compounds Ce_1-xLa_xBiPt

We report on the Fermi surface in the correlated half-Heusler compound Ce_1-xLa_xBiPt. 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 ca 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 4F electrons. Electronic band-structure calculations point to a 4f-polarization-induced change of the Fermi-surfache topology. In order to test this hypothesis, we have measured the (SdH) signal in a Ce_0.95La_0.05BiPt sample with a low La concentration.