The kagomé metals RbTi${}_3$Bi${}_5$ and CsTi${}_3$Bi${}_5$

The kagomé metals RbTi${}_3$Bi${}_5$ and CsTi${}_3$Bi${}_5$ were synthesized both as polycrystalline powders by heating the elements in an argon atmosphere and as single crystals grown using a self-flux method. The compounds crystallize in the hexagonal crystal system isotypically to KV${}_3$Sb${}_5$ (P6/mmm, Z = 1, CsTi${}_3$Bi${}_5$: a = 5.7873(1), c = 9.2062(1) Å; RbTi${}_3$Bi${}_5$: a = 5.773(1), c = 9.065(1) Å). The titanium atoms form a kagomé net with bismuth atoms in the hexagons as well as above and below the triangles. The alkali metal atoms are coordinated by 12 bismuth atoms and form AlB${}_2$-like slabs between the kagomé layers. Magnetic susceptibility measurements with CsTi${}_3$Bi${}_5$ and RbTi${}_3$Bi${}_5$ single crystals reveal Pauli-paramagnetism and traces of superconductivity caused by CsBi${}_2$/RbBi${}_2$ impurities. Magnetotransport measurements reveal conventional Fermi liquid behavior and quantum oscillations indicative of a single dominant orbit at low temperature. DFT calculations show the characteristic metallic kagomé band structure similar to that of CsV${}_3$Sb${}_5$ with reduced band filling. A symmetry analysis of the band structure does not reveal an obvious and unique signature of a nontrivial topology.