We use photoemission (PE) and x-ray absorption (XA) spectroscopy to study intercalation-induced changes in the electronic structure of β-HfNCl and ${\mathrm{Na}}_{0.22}\mathrm{HfNCl}.$ PE shows appearance of new states in ${\mathrm{Na}}_{0.22}\mathrm{HfNCl}$ within the gap of β-HfNCl, with negligible changes in the energy positions of valence-band features of the parent, suggesting a non-rigid-band behavior. N $1s$ XA results show that the tail of the conduction band, with a quasi-two-dimensional character, extends to lower energy in ${\mathrm{Na}}_{0.22}\mathrm{HfNCl}$ than in β-HfNCl. The study provides information on the electronic structure and its change across the insulator-to-metal transition of the new class of superconductors.

• Received 16 January 2001

DOI:https://doi.org/10.1103/PhysRevB.64.153107