Kagome metal GdNb 6 Sn 6 : A 4 d transition metal playground for topological magnetism and electron correlations

Magnetic kagome metals have garnered considerable attention as an ideal platform for investigating intrinsic topological structures, frustrated magnetism, and electron correlation effects. In this paper, we present the synthesis and detailed characterization of ${\mathrm{GdNb}}₆{\mathrm{Sn}}₆$, a metal that features a niobium-based kagome lattice and a frustrated triangular gadolinium network. The compound adopts the ${\mathrm{HfFe}}₆{\mathrm{Ge}}₆$-type crystal structure, with lattice parameters of $a=b=5.765(4)$ \AA{} and $c=9.536(8)$ \AA{}. Magnetic susceptibility and specific heat measurements reveal a magnetic transition $\ensuremath{\sim}2.3$ K. Electrical transport data confirm metallic behavior, unsaturated positive magnetoresistance, and a hole-dominated multiband Hall effect. Furthermore, first-principles calculations indicate that Nb-$4d$ orbitals predominantly contribute to the electronic states near the Fermi energy, with the band structure showing multiple topologically nontrivial crossings around the Fermi surface. We also compare ${\mathrm{GdNb}}₆{\mathrm{Sn}}₆$ with ${\mathrm{GdV}}₆{\mathrm{Sn}}₆$, highlighting their similarities and differences. Our findings pave the way for exploring $R{\mathrm{Nb}}₆{\mathrm{Sn}}₆$ ($R$ = rare earth) with customized substitutions of $R$ sites to fine-tune their properties.