Magnetotransport studies of Fe vacancy-ordered Fe 4+δ Se 5 nanowires

Significance This work reveals that Fe 4+δ Se 5 with ordered Fe vacancy is a nonoxide compound with the Verwey-like electronic correlation. Detailed measurements showing magnetic field-independent magnetoresistance at low temperature suggest it is in a charge-ordered state below T ≈ 17 K. The results of the field orientation measurements indicate that the spin-orbital coupling is crucial in √5 × √5 Fe vacancy-ordered Fe 4+δ Se 5 at low temperatures. Our findings provide valuable information to better understand the orbital nature and the interplay between the metal-insulator transition and superconductivity in FeSe-based materials.