Complex magnetic landscape in kagome metal TbTi₃Bi₄ and competition with family of Ln₂₋ₓTi₆₊ₓBi₉ (Ln: Tb-Lu) shurikagome metals

Here we present the discovery and characterization of TbTi₃Bi₄, the smallest rare-earth containing member of the LnTi₃Bi₄ family. We previously reported on the LnTi₃Bi₄ (Ln: La-Gd³⁺, Eu²⁺, Yb²⁺) kagome metals. This structure type represents a magnetically diverse and exfoliable family of kagome metals. Detailed characterization of the magnetic and electronic transport properties of TbTi₃Bi₄ reveals a highly complex landscape of magnetic phases arising from an antiferromagnetic ground state. A series of metamagnetic transitions creates at least 5 unique phase pockets, including a 1/3 and 2/3 magnetization plateau. Further, the system exhibits an intimate connection between the magnetism and magnetotransport, exhibiting sharp switching from positive (+40%) to negative magnetoresistance (-50%) near a metamagnetic transition. Unlike the Lu-Gd analogs, TbTi₃Bi₄ cannot be synthesized by the methodology presented previously due to phase competition with another, unreported class of materials, the Ln₂₋ₓTi₆₊ₓBi₉ (x~1.7-1.2) (Ln: Tb--Lu) shurikagome metals. Like the LnTi₃Bi₄ kagome metals, the Ln₂₋ₓTi₆₊ₓBi₉ family exhibits quasi-2D networks of titanium and chains of rare-earth. We present the structures and some select basic properties of the Ln₂₋ₓTi₆₊ₓBi₉ family alongside the newly discovered TbTi₃Bi₄. A discussion regarding the phase competition between the LnTi₃Bi₄ and Ln₂₋ₓTi₆₊ₓBi₉ families helps frame the difficulty in synthesizing LnTi₃Bi₄ compounds with small Ln species and provides a strategy to circumvent formation of Ln₂₋ₓTi₆₊ₓBi₉.