Electronic structure of NiS 1−x Se x across the phase transition

We report very highly resolved photoemission spectra of NiS 1−x Se x across the so-called metal-insulator transition as a function of temperature as well as composition. The present results convincingly demonstrate that the low temperature, antiferromagnetic phase is metallic, with a reduced density of states at E F . This decrease is due possibly to the opening of gaps along specific directions in the Brillouin zone caused by the antiferromagnetic ordering.