Tantalum arsenide is a compound of tantalum and arsenic with the formula TaAs. It is notable as being the first topological Weyl semimetal that was identified and characterized by ARPES.
Tantalum arsenide crystallizes in a body-centered tetragonal unit cell with lattice parameters a = 3.44 Å and c = 11.65 Å. It belongs to the space group I41md.
TaAs has been prepared by decomposing TaAs2 at 900 °C. A more recent preparation yielded large, single crystals of TaAs by chemical vapor transport with elemental precursors and iodine as the transport agent:
TaI5 (g) + AsI3 (g) ↔ TaAs (s) + 4 I2 (g)