Figure 1C shows the magnetic field dependence of the Nernst coefficients measured at 200 and 300 K. We first discuss our observation of the large ANE in Fe 3Sn. Besides, this system is made of naturally abundant, low-cost element and has a high Curie temperature of 760 K and thus is useful for designing the transverse thermoelectric conversion device ( Fig. Moreover, our first-principles calculations confirm that the large transverse thermoelectric conductivity,О± ji, comes from the Berry curvature notably enhanced along a flat hexagonal frame formed by a nodal plane. Comprehensive transport measurements show a large Nernst coefficient, reaching up to 3 ОјV K в€’1 around room temperature, 10 times higher than that in pure iron. In our study, we fabricated polycrystalline samples of Fe 3Sn D0 19 phase by arc melting method followed by a long period of annealing procedure (see Materials and Methods). Previous polycrystalline Fe 3Sn of hexagonal phase was synthesized by solid-state reaction method, and the product was very porous ( 20). This material has never been studied from the thermoelectric perspective, practically because of the difficulty of the synthesis ( 20, 26). Stacking two kagome layers with the half c axis separation and 60В° rotation composes the primitive unit cell ( Fig. In the ab plane, iron atoms form a kagome lattice, while the tin atoms occupy the center of each hexagon. This material has a hexagonal D0 19 type structure with the space group of P6 3/ mmc, the same as the antiferromagnetic Weyl semimetals Mn 3 X ( X = Sn or Ge), but differs from its two sibling compounds, tin-intercalated Fe-Sn binary compounds Fe 3Sn 2 and FeSn ( Fig. Our comprehensive studies using both experiment and theory reveal the nodal plane formed in the kagome magnet, Fe 3Sn. Here, we report the experimental observation of a room temperature high ANE and AHE in an iron-based binary ferromagnet based on the kagome lattice. However, the formation of such a nontrivial nodal plane near the Fermi level has never been studied to date. Such a вЂњnodal planeвЂќ would also have more advantages, by maximally contributing to the effective energy integral paths and by thus enhancing the Berry curvature and density of the states for spin up/down at the Fermi level in the first Brillouin zone (BZ) ( 10, 15). Following the concept behind these nodal points and lines produced by the band crossings ( 19), it would be highly interesting to consider even higher-dimensional crossings of the nondegenerate band producing a two-dimensional plane. Recent progresses have revealed that the intrinsic ANE can be enhanced by the crossing of nondegenerate flat bands producing nontrivial topological structure, such as the Lifshitz transitions between type-I and type-II Weyl semimetals and nodal web, leading to the ever-recorded largest value of 6 ОјV K в€’1 at room temperature in Co 2MnGa and Fe 3 X ( X = Ga and Al) ( 10, 11, 14, 15, 18). Great efforts have been made to enhance Berry curvature not only by the way of the first-principles calculations using the modern high-throughput methods ( 16) but also by introducing external conditions to split the degeneracy of the bands, for example, the centrosymmetry breaking induced by strain, resulting in the substantial net Berry curvature ( 17). Berry curvature, the fictitious magnetic field in momentum space, is the origin of various intrinsic transverse effects such as anomalous Hall effect (AHE), anomalous Nernst effect (ANE), and magneto-optical effects ( 1вЂ“ 15).

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