Transport anomalies in the layered compound BaPt4Se6.

We report a layered ternary selenide BaPt₄Se₆ featuring sesqui-selenide Pt₂Se₃ layers sandwiched by Ba atoms. The Pt₂Se₃ layers in this compound can be derived from the Dirac-semimetal PtSe₂ phase with Se vacancies that form a honeycomb structure. This structure results in a Pt (VI) and Pt (II) mixed-valence compound with both PtSe₆ octahedra and PtSe₄ square net coordination configurations. Temperature-dependent electrical transport measurements suggest two distinct anomalies: a resistivity crossover, mimic to the metal-insulator (M-I) transition at ~150 K, and a resistivity plateau at temperatures below 10 K. The resistivity crossover is not associated with any structural, magnetic, or charge order modulated phase transitions. Magnetoresistivity, Hall, and heat capacity measurements concurrently suggest an existing hidden state below 5 K in this system. Angle-resolved photoemission spectroscopy measurements reveal a metallic state and no dramatic reconstruction of the electronic structure up to 200 K. [ABSTRACT FROM AUTHOR]