Crystallographic Stability and No Evidence of Higher-Order Saddle Points in the HfFe 6 Ge 6 -type Kagome Metal ScCo 6 Ge 6

While kagome RT 6 X 6 (R = Li, Mg, Zr, and rare-earth metals; T = 3d transition metals; X = Ge/Sn) compounds are widely studied, Co-based RCo 6 X 6 phases remain largely limited to structural reports, with few systematic studies of their physical properties. Here we report Sn-flux-grown single-crystalline ScCo 6 Ge 6 and its structural and physical characterization. Single-crystal X-ray diffraction confirms that ScCo 6 Ge 6 adopts the HfFe 6 Ge 6 -type structure rather than the vacancy-driven Y 0.5 Co 3 Ge 3 -type variant. Across the RCo 6 Ge 6 series, structural preference correlates with the Shannon ionic radius of R (8-fold coordination), placing ScCo 6 Ge 6 within the stability range of the HfFe 6 Ge 6 -type framework. Magnetization exhibits weak temperature dependence consistent with Pauli-like paramagnetism. The resistivity is well described by a Bloch–Grüneisen form with a Debye temperature exceeding 230 K, consistent with phonon-dominated scattering. Electrical transport also shows a conventional linear Hall response and negligible magnetoresistance, indicative of simple metallic behavior. Electronic structure calculations identify a Ge-derived quadratic saddle point ∼0.35 eV below E F, with no evidence of higher-order saddle points near the Fermi level. These results highlight that crystallographic stability and physical properties in RCo 6 Ge 6 are governed not only by the Co kagome lattice but also sensitively by the Ge sublattice.