Electronic-structure evolution through the metal-insulator transition in (formula presented)

We performed a photoemission investigation of the electronic structure of (Formula presented) and (Formula presented) through the first order (paramagnetic) metal to (antiferromagnetic) insulator transition. Surprisingly, the data reveal a temperature-dependent loss of spectral weight near the chemical potential, which extends well below the coincident metal-insulator (Formula presented) and magnetic (Formula presented) transition temperatures. This is in contrast with the behavior in (Formula presented) and (Formula presented) where the two transitions are separate. The spectral properties clearly indicate two distinct regimes for (Formula presented) with (Formula presented) and (Formula presented)