Flat band in the multibandmetal MnSb${}_2$

Abstract

We report the realization of a metallic flat band in the marcasite compound MnSb${}_2$. The material was synthesized under high pressure, and its crystal structure was established by X-ray diffraction. Electrical and thermoelectric transport measurements reveal signatures of a flat band near the Fermi level that persist across three structural, magnetic, and electronic transitions. These observations are supported by extensive density-functional-theory calculations. Related marcasite diantimonides, including FeSb${}_2$ and CrSb${}_2$, also host flat bands, but these lie far from the Fermi level and therefore do not produce a metallic flat-band state. MnSb${}_2$ therefore emerges as the only known metallic marcasite antimonide in which a flat band lies in the vicinity of the Fermi level.