We have studied a charge-orbital driven metal-insulator transition (MIT) in hollandite-type Ba x Ti 8 O 16 + d by means of hard x-ray photoemission spectroscopy (HAXPES). The Ti 2 p HAXPES indicates strong Ti3 + / Ti 4 + 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 Ba x Ti 8 O 16 + d .
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