Single-crystal study of the charge density wave metal LuNiC2

We report on single crystal growth, single crystal x-ray diffraction, physical properties and density functional theory (DFT) electronic structure as well as Fermi surface calculations for two orthorhombic ternary carbides, LuCoC2 and LuNiC2. Electrical resistivity measurements reveal for LuNiC2 a Peierls-type charge density wave (CDW) transition at TP~450K and for T u003e TP a significant anisotropy of the electrical conductivity, which is highest along the orthorhombic a-axis. LuCoC2 displays a simple metallic behavior with neither CDW ordering nor superconductivity above 0.4 K. The formation of a significant gap due to CDW order in LuNiC2 is corroborated by specific heat measurements as compared to DFT calculations: experimental Sommerfeld coefficients, gamma= 5.9(1) mJ/molK2 for LuCoC2 and gamma = 0.83(5) mJ/molK2 for LuNiC2, are much more different than the calculated values of the electronic density of states at the Fermi level, N(Ef) = 1.62 states/eV f.u. for LuCoC2 and N(Ef) = 1.03 states/eV f.u. for LuNiC2. The large discrepancy between the experimental Sommerfeld coefficient of LuNiC2 and its calculated, bare band structure value (without CDW ordering), gamma_DFT = 2.43 mJ/molK2, suggests that the Fermi surface of LuNiC2 is strongly modified by CDW gap formation.