Al3Ta is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Ta(1) is bonded to four equivalent Al(1) and eight equivalent Al(2) atoms to form TaAl12 cuboctahedra that share corners with four equivalent Ta(1)Al12 cuboctahedra, corners with eight equivalent Al(1)Ta4Al8 cuboctahedra, edges with eight equivalent Ta(1)Al12 cuboctahedra, edges with sixteen equivalent Al(2)Ta4Al8 cuboctahedra, faces with four equivalent Ta(1)Al12 cuboctahedra, faces with six equivalent Al(1)Ta4Al8 cuboctahedra, and faces with eight equivalent Al(2)Ta4Al8 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Ta(1) and eight equivalent Al(2) atoms to form distorted AlTa4Al8 cuboctahedra that share corners with four equivalent Al(1)Ta4Al8 cuboctahedra, corners with eight equivalent Ta(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Ta4Al8 cuboctahedra, edges with sixteen equivalent Al(2)Ta4Al8 cuboctahedra, faces with four equivalent Al(1)Ta4Al8 cuboctahedra, faces with six equivalent Ta(1)Al12 cuboctahedra, and faces with eight equivalent Al(2)Ta4Al8 cuboctahedra. In the second Al site, Al(2) is bonded to four equivalent Ta(1), four equivalent Al(1), and four equivalent Al(2) atoms to form AlTa4Al8 cuboctahedra that share corners with twelve equivalent Al(2)Ta4Al8 cuboctahedra, edges with eight equivalent Ta(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Ta4Al8 cuboctahedra, edges with eight equivalent Al(2)Ta4Al8 cuboctahedra, faces with four equivalent Ta(1)Al12 cuboctahedra, faces with four equivalent Al(1)Ta4Al8 cuboctahedra, and faces with ten equivalent Al(2)Ta4Al8 cuboctahedra.
Al3Ta is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Ta(1) is bonded to four equivalent Al(1) and eight equivalent Al(2) atoms to form TaAl12 cuboctahedra that share corners with four equivalent Ta(1)Al12 cuboctahedra, corners with eight equivalent Al(1)Ta4Al8 cuboctahedra, edges with eight equivalent Ta(1)Al12 cuboctahedra, edges with sixteen equivalent Al(2)Ta4Al8 cuboctahedra, faces with four equivalent Ta(1)Al12 cuboctahedra, faces with six equivalent Al(1)Ta4Al8 cuboctahedra, and faces with eight equivalent Al(2)Ta4Al8 cuboctahedra. All Ta(1)-Al(1) bond lengths are 2.71 Å. All Ta(1)-Al(2) bond lengths are 2.86 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Ta(1) and eight equivalent Al(2) atoms to form distorted AlTa4Al8 cuboctahedra that share corners with four equivalent Al(1)Ta4Al8 cuboctahedra, corners with eight equivalent Ta(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Ta4Al8 cuboctahedra, edges with sixteen equivalent Al(2)Ta4Al8 cuboctahedra, faces with four equivalent Al(1)Ta4Al8 cuboctahedra, faces with six equivalent Ta(1)Al12 cuboctahedra, and faces with eight equivalent Al(2)Ta4Al8 cuboctahedra. All Al(1)-Al(2) bond lengths are 2.86 Å. In the second Al site, Al(2) is bonded to four equivalent Ta(1), four equivalent Al(1), and four equivalent Al(2) atoms to form AlTa4Al8 cuboctahedra that share corners with twelve equivalent Al(2)Ta4Al8 cuboctahedra, edges with eight equivalent Ta(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Ta4Al8 cuboctahedra, edges with eight equivalent Al(2)Ta4Al8 cuboctahedra, faces with four equivalent Ta(1)Al12 cuboctahedra, faces with four equivalent Al(1)Ta4Al8 cuboctahedra, and faces with ten equivalent Al(2)Ta4Al8 cuboctahedra. All Al(2)-Al(2) bond lengths are 2.71 Å.