CoBi3--the first binary compound of cobalt with bismuth: high-pressure synthesis and superconductivity.

The first compound in the cobalt bismuth system was synthesized by high-pressure high-temperature synthesis at 5 GPa and 450 °C. CoBi3 crystallizes in space group Pnma (no. 62) with lattice parameters of a = 8.8464(7) Å, b = 4.0697(4) Å and c = 11.5604(9) Å adopting a NiBi3-type crystal structure. CoBi3 undergoes a superconducting transition at Tc = 0.48(3) K as evidenced by electrical-resistivity and specific-heat measurements. Based on the anomaly of the specific heat at Tc and considering the estimated electron-phonon coupling, the new Bi-rich compound can be classified as a Bardeen-Cooper-Schrieffer-type superconductor with weak electron-phonon coupling. Density-functional theory calculations disclose a sizable influence of the spin-orbit coupling to the valence states and proximity to a magnetic instability, which accounts for a significantly enhanced Sommerfeld coefficient.

Magnetic and magnetocaloric properties of the high-temperature modification of TbTiGe.

The high-temperature form (HT) of the ternary germanide TbTiGe was prepared by melting. The investigation of HT-TbTiGe by x-ray and neutron powder diffractions shows that the compound crystallizes in the tetragonal CeScSi-type structure (space group I4/mmm; a = 404.84(5) and c = 1530.10(9) pm as unit cell parameters). Magnetization and specific heat measurements as well as neutron powder diffraction performed on HT-TbTiGe reveal a ferromagnet having T(C) = 300(1) K as the Curie temperature; the Tb-moments are aligned along the c-axis. This magnetic ordering is associated with a modest magnetocaloric effect around room temperature. The isothermal magnetic entropy change ΔS(m) was determined from the magnetization data; ΔS(m) reaches, respectively, a maximum value of  - 4.3 and  - 2.0 J K(-1) kg(-1) for a magnetic field change of 5 and 2 T.