Electronic band structure and Fermi surface of CaB6 studied by angle-resolved photoemission spectroscopy.

We report high-resolution angle-resolved photoemission spectroscopy (ARPES) on CaB 6 . The band structure determined by ARPES shows a 1 eV energy gap at the X point between the valence and the conduction bands. We found a small electron pocket at the X point, whose carrier number is estimated to be (4-5) X 10 1 9 cm - 3 , in good agreement with the Hall resistivity measurement with the same crystal. The experimental results are discussed in comparison with band structure calculations and theoretical models for the high-temperature ferromagnetism.