A large anomalous Nernst effect (ANE) is crucial for thermoelectric energy conversion applications because the associated unique transverse geometry facilitates module fabrication. Topological ferromagnets with large Berry curvatures show large ANEs; however, they face drawbacks such as strong magnetic disturbances and low mobility due to high magnetization. Herein, we demonstrate that YbMnBi2, a canted antiferromagnet, has a large ANE conductivity of ~10 A m−1 K−1 that surpasses large values observed in other ferromagnets (3–5 A m−1 K−1). The canted spin structure of Mn guarantees a non-zero Berry curvature, but generates only a weak magnetization three orders of magnitude lower than that of general ferromagnets. The heavy Bi with a large spin–orbit coupling enables a large ANE and low thermal conductivity, whereas its highly dispersive px/y orbitals ensure low resistivity. The high anomalous transverse thermoelectric performance and extremely small magnetization make YbMnBi2 an excellent candidate for transverse thermoelectrics.

SnSe is a semiconductor compound reported to possess very high thermoelectric ZT values at 600 °C to 700 °C. Oxidation and sublimation are of significant concern at such temperatures. The oxidation behavior of SnSe at four temperatures between 600 °C and 700 °C in atmospheric air was investigated by monitoring the weight change as a function of time as well as by characterizing the oxidized samples using optical microscopy, SEM with EDS, and powder XRD. The results show that SnSe oxidizes very rapidly at 600 °C to 700 °C to form SnO 2 and possibly Sn(SeO 3) 2. Sublimation of Se and Se oxides is also observed. At 600 °C the consumption of Sn from SnSe to form SnO 2 drives the composition to Se rich. A layer of SnSe 2 forms between the oxides and SnSe. At ≥ 650 °C the consumption of Sn likely leads to the formation of a transient liquid phase which significantly accelerates both oxidation and sublimation. It is concluded that SnSe needs to be used under vacuum or with a protective coating such as pure Si.

Valley anisotropy is a favorable electronic structure feature that could be utilized for good thermoelectric performance. Here, taking advantage of the single anisotropic Fermi pocket in p-type Mg3Sb2, a feasible strategy utilizing the valley anisotropy to enhance the thermoelectric power factor is demonstrated by synergistic studies on both single crystals and textured polycrystalline samples. Compared to the heavy-band direction, a higher carrier mobility by a factor of 3 is observed along the light-band direction, while the Seebeck coefficient remains similar. Together with lower lattice thermal conductivity, an increased room-temperature zT by a factor of 3.6 is found. Moreover, the first-principles calculations of 66 isostructural Zintl phase compounds are conducted and 9 of them are screened out displaying a pz-orbital-dominated valence band, similar to Mg3Sb2. In this work, we experimentally demonstrate that valley anisotropy is an effective strategy for the enhancement of thermoelectric performance in materials with anisotropic Fermi pockets.

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