Fermi level pinning of a massive electron state in YbBiPt

The electronic structure of the heavy fermion compound YbBiPt is investigated using energy band calculations which account for strong on-site f-electron Coulomb correlations. We find that in the very low free-electron-like density near the Fermi level one extremely narrow 4f state becomes pinned at the Fermi energy E-F. The pinned 4f state gives,in the presence of antiferromagnetism, rise to massive electron behavior for which we calculate an unenhanced Sommerfeld constant of 0.25 J mol(-1) K-2 maximally.