Interplay of magnetism and correlated electron behavior in the kagome metal TbNb₆Sn₆

Kagome-based magnetic metals are recognized as exemplary systems for the study of quantum materials, offering a distinctive framework to investigate the interrelation of topologically nontrivial electronic structures, geometrically frustrated magnetic moments (f ≈ 7), and strongly correlated electron phenomena. The growth and detailed analysis of the 4d kagome metal TbNb₆Sn₆ are reported, in which a kagome network of Nb atoms is integrated with a triangularly frustrated arrangement of localized Tb³⁺ moments. High-quality crystals are found to adopt the centrosymmetric HfFe₆Ge₆-type structure (P6/mmm), with lattice constants precisely refined to a = b = 5.757 91 Å and c = 9.555 20 Å. Striking uniaxial anisotropy is revealed by magnetization measurements, with the magnetic susceptibility along the c direction exceeding the in-plane susceptibility by nearly 50-fold just above 3 K, indicating a strong out-of-plane alignment preference of the Tb³⁺ 4 f moments. Two successive magnetic transitions are observed at zero magnetic field at T_N = 2.91 K and T₂ = 2.32 K. When a magnetic field is applied along the c direction, four distinct metamagnetic transitions are observed at low temperatures, culminating in a fully polarized moment of 8.24 μ_B/Tb ion at 2 K above 3.6 T, as evidenced by both magnetization and resistivity measurements. A positive, nonsaturating magnetoresistance and a nonlinear Hall effect are exhibited by the compound across the full temperature range studied. First-principles calculations show that the Fermi level is dominated by Nb 4d orbitals, which generate kagome-derived bands featuring Dirac crossings and Van Hove singularities indicative of nontrivial topology. The potential of the RNb₆Sn₆ family as a versatile platform for realizing emergent quantum states is highlighted by the combination of tunable magnetic anisotropy, complex spin textures, and multiband conduction.