BaHo4Si5O17 crystallizes in the monoclinic P2_1/m space group. Ba(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(10), one O(5), two equivalent O(6), and two equivalent O(8) atoms to form distorted HoO6 pentagonal pyramids that share corners with three equivalent Si(2)O4 tetrahedra, corners with three equivalent Si(3)O4 tetrahedra,  an edgeedge with one Ho(2)O6 octahedra, and edges with two equivalent Ho(1)O6 pentagonal pyramids. In the second Ho site, Ho(2) is bonded to one O(1), one O(10), one O(2), one O(4), one O(5), and one O(7) atom to form distorted HoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra,  an edgeedge with one Ho(2)O6 octahedra, and  an edgeedge with one Ho(1)O6 pentagonal pyramid. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Ho(2)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-54°. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Ho(2)O6 octahedra, corners with three equivalent Ho(1)O6 pentagonal pyramids, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-51°. In the third Si site, Si(3) is bonded to one O(10), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Ho(2)O6 octahedra, corners with three equivalent Ho(1)O6 pentagonal pyramids, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-58°. There are ten inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ho(1), one Ho(2), and one Si(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to two equivalent Ho(1) and one Si(2) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to one Ba(1), one Ho(2), and one Si(3) atom. In the fourth O site, O(8) is bonded in a distorted trigonal planar geometry to two equivalent Ho(1) and one Si(3) atom. In the fifth O site, O(9) is bonded in a linear geometry to two equivalent Si(3) atoms. In the sixth O site, O(10) is bonded in a distorted trigonal planar geometry to one Ho(1), one Ho(2), and one Si(3) atom. In the seventh O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ho(2), and one Si(1) atom. In the eighth O site, O(2) is bonded in a 1-coordinate geometry to one Ba(1), two equivalent Ho(2), and one Si(1) atom. In the ninth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. In the tenth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(1), one Ho(2), and one Si(2) atom.
BaHo4Si5O17 crystallizes in the monoclinic P2_1/m space group. Ba(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms. The Ba(1)-O(1) bond length is 2.94 Å. The Ba(1)-O(2) bond length is 2.98 Å. Both Ba(1)-O(3) bond lengths are 3.12 Å. Both Ba(1)-O(4) bond lengths are 2.71 Å. Both Ba(1)-O(7) bond lengths are 2.86 Å. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(10), one O(5), two equivalent O(6), and two equivalent O(8) atoms to form distorted HoO6 pentagonal pyramids that share corners with three equivalent Si(2)O4 tetrahedra, corners with three equivalent Si(3)O4 tetrahedra,  an edgeedge with one Ho(2)O6 octahedra, and edges with two equivalent Ho(1)O6 pentagonal pyramids. The Ho(1)-O(10) bond length is 2.26 Å. The Ho(1)-O(5) bond length is 2.35 Å. There is one shorter (2.23 Å) and one longer (2.32 Å) Ho(1)-O(6) bond length. Both Ho(1)-O(8) bond lengths are 2.25 Å. In the second Ho site, Ho(2) is bonded to one O(1), one O(10), one O(2), one O(4), one O(5), and one O(7) atom to form distorted HoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra,  an edgeedge with one Ho(2)O6 octahedra, and  an edgeedge with one Ho(1)O6 pentagonal pyramid. The Ho(2)-O(1) bond length is 2.31 Å. The Ho(2)-O(10) bond length is 2.26 Å. The Ho(2)-O(2) bond length is 2.39 Å. The Ho(2)-O(4) bond length is 2.21 Å. The Ho(2)-O(5) bond length is 2.30 Å. The Ho(2)-O(7) bond length is 2.20 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Ho(2)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-54°. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(2) bond length is 1.64 Å. Both Si(1)-O(3) bond lengths are 1.66 Å. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Ho(2)O6 octahedra, corners with three equivalent Ho(1)O6 pentagonal pyramids, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-51°. The Si(2)-O(3) bond length is 1.70 Å. The Si(2)-O(4) bond length is 1.63 Å. The Si(2)-O(5) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.64 Å. In the third Si site, Si(3) is bonded to one O(10), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Ho(2)O6 octahedra, corners with three equivalent Ho(1)O6 pentagonal pyramids, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-58°. The Si(3)-O(10) bond length is 1.66 Å. The Si(3)-O(7) bond length is 1.63 Å. The Si(3)-O(8) bond length is 1.64 Å. The Si(3)-O(9) bond length is 1.64 Å. There are ten inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ho(1), one Ho(2), and one Si(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to two equivalent Ho(1) and one Si(2) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to one Ba(1), one Ho(2), and one Si(3) atom. In the fourth O site, O(8) is bonded in a distorted trigonal planar geometry to two equivalent Ho(1) and one Si(3) atom. In the fifth O site, O(9) is bonded in a linear geometry to two equivalent Si(3) atoms. In the sixth O site, O(10) is bonded in a distorted trigonal planar geometry to one Ho(1), one Ho(2), and one Si(3) atom. In the seventh O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ho(2), and one Si(1) atom. In the eighth O site, O(2) is bonded in a 1-coordinate geometry to one Ba(1), two equivalent Ho(2), and one Si(1) atom. In the ninth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. In the tenth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(1), one Ho(2), and one Si(2) atom.