The layered metal Ti2PTe2

Crystals of Ti2PTe2 have been synthesised by chemical vapour transport. Ti2PTe2 crystallises, isostructural to the mineral tetradymite (Bi2STe2), in the space group R3-bar m with unit-cell parameters a=3.6387(2) A and c=28.486(2) A for the hexagonal setting. In the structure, layers of isolated phosphide and telluride anions form an ordered close sphere-packing with titanium cations filling two-thirds of the octahedral voids. From XANES fluorescence, the presence of Ti4+ is clearly established. In accordance with the ionic formula (Ti4+)2(P3-)(Te2-)2(e-) metallic conductivity (ρ=40 μΩ cm at 300 K) and nearly temperature-independent paramagnetism are found. The electronic band structure shows bands of titanium states crossing the Fermi level in directions corresponding to the ab-plane and a band gap along the c-axis. - Graphical abstract: Crystal structure of Ti2PTe2 with stacking sequence of the hexagonal layers of anions and cations. Highlighted in red is the octahedral coordination of phosphorus by titanium, and in grey the octahedral coordination of titanium by phosphorus and tellurium