Unusual Charge Density Wave coupled to a metal-to-metal transition in Ce₃Co₄Sn₁₃

We study the electronic structure of the skutterudite Ce₃Co₄Sn₁₃, which exhibits a charge density wave transition (CDW ; T_CDW∼160 K) coupled to a metal-to-metal transition. We use temperature dependent HAXPES and XAS to investigate the occupied and unoccupied electronic states of Ce₃Co₄Sn₁₃. The Co 2p and Sn 3p core level spectra show small but finite shifts in energy positions across T_CDW but Ce 3d core level spectra do not show any change across the transition. The Ce M-edge XAS spectrum compared with calculations indicate a typical trivalent ionic Ce³⁺ spectral shape, ruling out Kondo screening in Ce₃Co₄Sn₁₃. In contrast, the Co 2p L-edge XAS spectrum compared with calculations shows evidence for hybridization with neighbouring Sn atoms in a trigonal prismatic co-ordination. Temperature dependent XAS across the Co 2p L-edge shows a small shift across T_CDW, consistent with HAXPES results. The Co 3d states are observed at a binding energy of ∼2 eV while the Ce 4f states occurs within 0.5 eV of the Fermi level as a weak feature. The results indicate an unusual CDW coupled to a metal-to-metal transition in Ce₃Co₄Sn₁₃.