Sr3Ga2As4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to two equivalent As(2) and four equivalent As(1) atoms. In the second Sr site, Sr(2) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form distorted SrAs6 octahedra that share corners with four equivalent Ga(1)As4 tetrahedra, edges with two equivalent Sr(2)As6 octahedra, and edges with four equivalent Ga(1)As4 tetrahedra. Ga(1) is bonded to two equivalent As(1) and two equivalent As(2) atoms to form distorted GaAs4 tetrahedra that share corners with two equivalent Sr(2)As6 octahedra, corners with two equivalent Ga(1)As4 tetrahedra, edges with two equivalent Sr(2)As6 octahedra, and  an edgeedge with one Ga(1)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-56°. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Sr(2), four equivalent Sr(1), and two equivalent Ga(1) atoms to form distorted AsSr5Ga2 pentagonal bipyramids that share corners with two equivalent As(1)Sr5Ga2 pentagonal bipyramids, corners with four equivalent As(2)Sr4Ga2 pentagonal pyramids, edges with five equivalent As(1)Sr5Ga2 pentagonal bipyramids, edges with six equivalent As(2)Sr4Ga2 pentagonal pyramids, and  a faceface with one As(1)Sr5Ga2 pentagonal bipyramid. In the second As site, As(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Ga(1) atoms to form distorted AsSr4Ga2 pentagonal pyramids that share corners with four equivalent As(1)Sr5Ga2 pentagonal bipyramids, corners with two equivalent As(2)Sr4Ga2 pentagonal pyramids, edges with six equivalent As(1)Sr5Ga2 pentagonal bipyramids, and edges with four equivalent As(2)Sr4Ga2 pentagonal pyramids.
Sr3Ga2As4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to two equivalent As(2) and four equivalent As(1) atoms. There is one shorter (3.08 Å) and one longer (3.10 Å) Sr(1)-As(2) bond length. There are a spread of Sr(1)-As(1) bond distances ranging from 3.19-3.54 Å. In the second Sr site, Sr(2) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form distorted SrAs6 octahedra that share corners with four equivalent Ga(1)As4 tetrahedra, edges with two equivalent Sr(2)As6 octahedra, and edges with four equivalent Ga(1)As4 tetrahedra. Both Sr(2)-As(1) bond lengths are 3.24 Å. There are two shorter (3.07 Å) and two longer (3.12 Å) Sr(2)-As(2) bond lengths. Ga(1) is bonded to two equivalent As(1) and two equivalent As(2) atoms to form distorted GaAs4 tetrahedra that share corners with two equivalent Sr(2)As6 octahedra, corners with two equivalent Ga(1)As4 tetrahedra, edges with two equivalent Sr(2)As6 octahedra, and  an edgeedge with one Ga(1)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-56°. There is one shorter (2.53 Å) and one longer (2.55 Å) Ga(1)-As(1) bond length. There is one shorter (2.47 Å) and one longer (2.49 Å) Ga(1)-As(2) bond length. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Sr(2), four equivalent Sr(1), and two equivalent Ga(1) atoms to form distorted AsSr5Ga2 pentagonal bipyramids that share corners with two equivalent As(1)Sr5Ga2 pentagonal bipyramids, corners with four equivalent As(2)Sr4Ga2 pentagonal pyramids, edges with five equivalent As(1)Sr5Ga2 pentagonal bipyramids, edges with six equivalent As(2)Sr4Ga2 pentagonal pyramids, and  a faceface with one As(1)Sr5Ga2 pentagonal bipyramid. In the second As site, As(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Ga(1) atoms to form distorted AsSr4Ga2 pentagonal pyramids that share corners with four equivalent As(1)Sr5Ga2 pentagonal bipyramids, corners with two equivalent As(2)Sr4Ga2 pentagonal pyramids, edges with six equivalent As(1)Sr5Ga2 pentagonal bipyramids, and edges with four equivalent As(2)Sr4Ga2 pentagonal pyramids.