YbBiPt (ytterbium-bismuth-platinum; also named YbPtBi) is an intermetallic material which at low temperatures exhibits an extremely high value of specific heat, which is a characteristic of heavy-fermion behavior.
YbBiPt was discovered by Zachary Fisk (Los Alamos National Laboratory) and coworkers in 1991 in the context of material research devoted to correlated electron systems such as heavy-fermion metals and Kondo insulators.
YbBiPt exhibits metallic behavior, e.g. continuously decreasing electrical resistivity upon cooling.
The temperature dependence of the specific heat shows an anomaly at 0.4K and linear behavior at yet lower temperatures with the enormous Sommerfeld coefficient (which describes the linear-in-temperature contribution to the specific heat caused by metallic electrons) of 8J/(mol Yb K2),[2] which indicates an effective mass of the charge carriers that is extremely large even for heavy-fermion standards.
The crystal structure of YbBiPt makes it an example of the Heusler compounds,[4] more precisely of the so-called half-Heuslers which have XYZ composition.