We have studied a charge-orbital driven metal-insulator transition (MIT) in hollandite-type BaxTi8O16+δ by means of hard x-ray photoemission spectroscopy (HAXPES). The Ti 2p HAXPES indicates strong Ti3+/Ti4+ charge fluctuation in the metallic phase above the MIT temperature. The metallic phase is characterized by a power-law spectral function near the Fermi level which would be a signature of bad metal with non-Drude polaronic behavior. The power-law spectral shape is associated with the large Seebeck coefficient of the metallic phase in BaxTi8O16+δ.
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