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TcGa crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Tc3- is bonded to six equivalent Tc3- and six equivalent Ga3+ atoms to form a mixture of distorted corner, edge, and face-sharing TcGa6Tc6 cuboctahedra. All Tc–Tc bond lengths are 2.90 Å. All Tc–Ga bond lengths are 2.64 Å. Ga3+ is bonded in a 6-coordinate geometry to six equivalent Tc3- atoms.
TcGa3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tc is bonded to twelve Ga atoms to form TcGa12 cuboctahedra that share corners with four equivalent TcGa12 cuboctahedra, corners with eight equivalent GaGa8Tc4 cuboctahedra, edges with eight equivalent TcGa12 cuboctahedra, edges with sixteen equivalent GaGa8Tc4 cuboctahedra, faces with four equivalent TcGa12 cuboctahedra, and faces with fourteen GaGa8Tc4 cuboctahedra. There are four shorter (2.72 Å) and eight longer (2.80 Å) Tc–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded to four equivalent Tc and eight Ga atoms to form GaGa8Tc4 cuboctahedra that share corners with twelve equivalent GaGa8Tc4 cuboctahedra, edges with eight equivalent TcGa12 cuboctahedra, edges with sixteen GaGa8Tc4 cuboctahedra, faces with four equivalent TcGa12 cuboctahedra, and faces with fourteen GaGa8Tc4 cuboctahedra. There are four shorter (2.72 Å) and four longer (2.80 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded to four equivalent Tc and eight equivalent Ga atoms to form GaGa8Tc4 cuboctahedra that share corners with four equivalent GaGa8Tc4 cuboctahedra, corners with eight equivalent TcGa12 cuboctahedra, edges with twenty-four GaGa8Tc4 cuboctahedra, faces with six equivalent TcGa12 cuboctahedra, and faces with twelve GaGa8Tc4 cuboctahedra.