Unconventional anomalous Hall effect and large anomalous Nernst effect in antiferromagnet SmMnBi2

The anomalous Hall effect (AHE) and its thermoelectric counterpart, the anomalous Nernst effect (ANE), are two transverse transport coefficients that are intensely studied in condensed matter physics. While conventional wisdom links AHE and ANE to ferromagnetism, recent achievements reveal that they can emerge in nonmagnetic and antiferromagnetic topological materials with a diversity of mechanisms—many of which await further elucidation. Here, both an unconventional AHE (UAHE) that does not scale with the magnetization and a sizable ANE ( ≈ 1.8 μV K−1) are shown to be possessed by the metallic tetragonal antiferromagnet SmMnBi2. Electronic band structure of SmMnBi2 is investigated by angle-resolved photoemission spectroscopy and first-principles calculations. It is demonstrated that the UAHE reflects the intrinsic Berry curvature contribution stemming from the spin-canted antiferromagnetism, whereas the ANE is possibly further amplified by extrinsic mechanisms. These results identify SmMnBi2 as a promising candidate for exploring unusual transverse transport effects and the extremely rich underlying physics. The anomalous Hall effect and anomalous Nernst effect are signature transport features for exploring the physics of magnetic topological phases. Here, an anomalous Nernst effect of 1.8 ≈μV/K and an unconventional anomalous Hall effect which does not scale with the magnetization are observed in a metallic tetragonal antiferromagnet.