Intricate Magnetic Landscape in Antiferromagnetic Kagome Metal TbTi₃Bi₄ and Interplay with Ln_2–xTi_6+xBi₉ (Ln: Tb···Lu) Shurikagome Metals

Here we present the discovery and characterization of the kagome metal TbTi₃Bi₄ in tandem with a new series of compounds, the Ln_2–xTi_6+xBi₉ (Ln: Tb–Lu) shurikagome metals. We previously reported on the growth of the LnTi₃Bi₄ (Ln: La–Gd³⁺, Eu²⁺, Yb²⁺) family, a chemically diverse and exfoliable series of kagome metals with complex and highly anisotropic magnetism. However, unlike the La–Gd analogs, TbTi₃Bi₄ cannot be synthesized by our previous methodology due to phase competition with crystals of Ln_2–xTi_6+xBi₉ (x ∼ 1.7–1.2). Here we discuss the phase competition between the LnTi₃Bi₄ and Ln_2–xTi_6+xBi₉ families, helping to frame the difficulty in synthesizing LnTi₃Bi₄ compounds with small Ln species and providing a strategy to circumvent the formation of Ln_2–xTi_6+xBi₉. Detailed characterization of the magnetic and electronic transport properties on single crystals 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 magnetic 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%). Like the LnTi₃Bi₄ kagome metals, the Ln_2–xTi_6+xBi₉ family exhibits quasi-2D networks of titanium and chains of rare earth. We present the structures and some basic magnetic properties of the Ln_2–xTi_6+xBi₉ family alongside our characterization of the newly discovered TbTi₃Bi₄.