Nb2SiAs2 crystallizes in the tetragonal P4/mmm space group. Nb(1) is bonded to four equivalent Nb(1), one Si(1), and one As(1) atom to form distorted NbNb4SiAs octahedra that share  a cornercorner with one As(1)NbAs5 octahedra, corners with five equivalent Nb(1)Nb4SiAs octahedra, edges with four equivalent Nb(1)Nb4SiAs octahedra, edges with four equivalent Si(1)Nb2Si4 octahedra, and edges with four equivalent As(1)NbAs5 octahedra. The corner-sharing octahedra are not tilted. Si(1) is bonded to two equivalent Nb(1) and four equivalent Si(1) atoms to form distorted SiNb2Si4 octahedra that share corners with two equivalent As(1)NbAs5 octahedra, corners with four equivalent Si(1)Nb2Si4 octahedra, edges with four equivalent Si(1)Nb2Si4 octahedra, and edges with eight equivalent Nb(1)Nb4SiAs octahedra. The corner-sharing octahedra are not tilted. As(1) is bonded to one Nb(1) and five equivalent As(1) atoms to form distorted AsNbAs5 octahedra that share  a cornercorner with one Nb(1)Nb4SiAs octahedra,  a cornercorner with one Si(1)Nb2Si4 octahedra, corners with four equivalent As(1)NbAs5 octahedra, edges with four equivalent Nb(1)Nb4SiAs octahedra, and edges with eight equivalent As(1)NbAs5 octahedra. The corner-sharing octahedra are not tilted.
Nb2SiAs2 crystallizes in the tetragonal P4/mmm space group. Nb(1) is bonded to four equivalent Nb(1), one Si(1), and one As(1) atom to form distorted NbNb4SiAs octahedra that share  a cornercorner with one As(1)NbAs5 octahedra, corners with five equivalent Nb(1)Nb4SiAs octahedra, edges with four equivalent Nb(1)Nb4SiAs octahedra, edges with four equivalent Si(1)Nb2Si4 octahedra, and edges with four equivalent As(1)NbAs5 octahedra. The corner-sharing octahedra are not tilted. All Nb(1)-Nb(1) bond lengths are 2.70 Å. The Nb(1)-Si(1) bond length is 2.57 Å. The Nb(1)-As(1) bond length is 2.77 Å. Si(1) is bonded to two equivalent Nb(1) and four equivalent Si(1) atoms to form distorted SiNb2Si4 octahedra that share corners with two equivalent As(1)NbAs5 octahedra, corners with four equivalent Si(1)Nb2Si4 octahedra, edges with four equivalent Si(1)Nb2Si4 octahedra, and edges with eight equivalent Nb(1)Nb4SiAs octahedra. The corner-sharing octahedra are not tilted. All Si(1)-Si(1) bond lengths are 2.70 Å. As(1) is bonded to one Nb(1) and five equivalent As(1) atoms to form distorted AsNbAs5 octahedra that share  a cornercorner with one Nb(1)Nb4SiAs octahedra,  a cornercorner with one Si(1)Nb2Si4 octahedra, corners with four equivalent As(1)NbAs5 octahedra, edges with four equivalent Nb(1)Nb4SiAs octahedra, and edges with eight equivalent As(1)NbAs5 octahedra. The corner-sharing octahedra are not tilted. There are four shorter (2.70 Å) and one longer (2.82 Å) As(1)-As(1) bond length.