Divalent Yb in the Ca$_3$Pd$_4$Bi$_8$ Structure Type: Crystal Growth and Physical Properties of Yb$_3$Pd$_4$Bi$_8$

Overview & Synopsis

We report on the single-crystal growth, crystal structure, and physical properties of Yb$_3$Pd$_4$Bi$_8$. Single crystal x-ray diffraction shows that the material crystallizes in the Ca$_3$Pd$_4$Bi$_8$ structure-type at ambient conditions, described by orthorhombic symmetry $Pbam$. Magnetization measurements reveal a nearly isotropic diamagnetic response, indicating that Yb is stabilized in a non-magnetic divalent configuration. Electrical resistivity measurements show a metallic behavior. First-principles calculations including spin--orbit coupling describe a metal whose states at the Fermi level are dominated by Bi $6p$ orbitals, with a density of states within 1% of that of the isoelectronic compound Ca$_3$Pd$_4$Bi$_8$, consistent with a filled and chemically inert $4f$ shell. They further show that the nonsymmorphic symmetry of the crystal enforces fourfold-degenerate nodal lines on the Brillouin-zone boundary, four of which cross the Fermi level and give symmetry-enforced Dirac points with a linear transverse dispersion. Despite strong metallic and covalent bonding within the Pd-Bi network, Yb$_3$Pd$_4$Bi$_8$ is realized as a rare-earth analog of the Ca$_3$Pd$_4$Bi$_8$ structure type with divalent Yb ions. This result offers a potential avenue to discover other rare-earth analogs within this structural family.