Photoemission study of the Kondo insulator Ce₃Bi₄Pt₃

The electronic structure of the Kondo insulator Ce₃Bi₄Pt₃ has been studied by high-resolution photoelectron spectroscopy. Indications of the unusual electronic structure are observed: the 4f derived peak near the Fermi level is located at a binding energy of 20 meV and is not cut-off by the Fermi edge as in conventional Kondo systems; for low photon energies, where the 4f contribution is negligible and the conduction band states are probed, a loss of spectral intensity in the same energy range is observed. These observations are related to the opening of a gap at low temperature, confirming the picture that hybridisation between a localised 4f state and the conduction band is responsible for the insulating character of this material.