Ca3Au9Ge2 crystallizes in the orthorhombic Pnnm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 16-coordinate geometry to two equivalent Au(1), two equivalent Au(5), three equivalent Au(2), three equivalent Au(3), three equivalent Au(4), and three equivalent Ge(1) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent Au(2), two equivalent Au(3), four equivalent Au(1), and four equivalent Au(4) atoms. There are five inequivalent Au sites. In the first Au site, Au(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Au(4), two equivalent Au(2), two equivalent Au(3), two equivalent Au(5), and one Ge(1) atom to form distorted AuCa4GeAu7 cuboctahedra that share corners with four equivalent Au(1)Ca4GeAu7 cuboctahedra,  an edgeedge with one Au(1)Ca4GeAu7 cuboctahedra, faces with two equivalent Au(5)Ca4Au8 cuboctahedra, and faces with three equivalent Au(1)Ca4GeAu7 cuboctahedra. In the second Au site, Au(2) is bonded in a 4-coordinate geometry to one Ca(2), three equivalent Ca(1), one Au(5), two equivalent Au(1), and one Ge(1) atom. In the third Au site, Au(3) is bonded in a 10-coordinate geometry to one Ca(2), three equivalent Ca(1), one Au(4), one Au(5), two equivalent Au(1), and two equivalent Ge(1) atoms. In the fourth Au site, Au(4) is bonded in a 1-coordinate geometry to two equivalent Ca(2), three equivalent Ca(1), one Au(1), one Au(3), and one Ge(1) atom. In the fifth Au site, Au(5) is bonded to four equivalent Ca(1), two equivalent Au(2), two equivalent Au(3), and four equivalent Au(1) atoms to form AuCa4Au8 cuboctahedra that share faces with two equivalent Au(5)Ca4Au8 cuboctahedra and faces with four equivalent Au(1)Ca4GeAu7 cuboctahedra. Ge(1) is bonded in a 8-coordinate geometry to three equivalent Ca(1), one Au(1), one Au(2), one Au(4), and two equivalent Au(3) atoms.
Ca3Au9Ge2 crystallizes in the orthorhombic Pnnm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 16-coordinate geometry to two equivalent Au(1), two equivalent Au(5), three equivalent Au(2), three equivalent Au(3), three equivalent Au(4), and three equivalent Ge(1) atoms. There is one shorter (3.19 Å) and one longer (3.23 Å) Ca(1)-Au(1) bond length. Both Ca(1)-Au(5) bond lengths are 3.39 Å. There are two shorter (3.11 Å) and one longer (3.62 Å) Ca(1)-Au(2) bond length. There are two shorter (3.29 Å) and one longer (3.43 Å) Ca(1)-Au(3) bond length. There are two shorter (3.24 Å) and one longer (3.71 Å) Ca(1)-Au(4) bond length. There are two shorter (3.20 Å) and one longer (3.26 Å) Ca(1)-Ge(1) bond length. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent Au(2), two equivalent Au(3), four equivalent Au(1), and four equivalent Au(4) atoms. Both Ca(2)-Au(2) bond lengths are 3.18 Å. Both Ca(2)-Au(3) bond lengths are 3.07 Å. All Ca(2)-Au(1) bond lengths are 3.54 Å. All Ca(2)-Au(4) bond lengths are 3.25 Å. There are five inequivalent Au sites. In the first Au site, Au(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Au(4), two equivalent Au(2), two equivalent Au(3), two equivalent Au(5), and one Ge(1) atom to form distorted AuCa4GeAu7 cuboctahedra that share corners with four equivalent Au(1)Ca4GeAu7 cuboctahedra,  an edgeedge with one Au(1)Ca4GeAu7 cuboctahedra, faces with two equivalent Au(5)Ca4Au8 cuboctahedra, and faces with three equivalent Au(1)Ca4GeAu7 cuboctahedra. The Au(1)-Au(4) bond length is 2.83 Å. Both Au(1)-Au(2) bond lengths are 2.91 Å. Both Au(1)-Au(3) bond lengths are 2.88 Å. Both Au(1)-Au(5) bond lengths are 2.98 Å. The Au(1)-Ge(1) bond length is 2.76 Å. In the second Au site, Au(2) is bonded in a 4-coordinate geometry to one Ca(2), three equivalent Ca(1), one Au(5), two equivalent Au(1), and one Ge(1) atom. The Au(2)-Au(5) bond length is 2.78 Å. The Au(2)-Ge(1) bond length is 2.55 Å. In the third Au site, Au(3) is bonded in a 10-coordinate geometry to one Ca(2), three equivalent Ca(1), one Au(4), one Au(5), two equivalent Au(1), and two equivalent Ge(1) atoms. The Au(3)-Au(4) bond length is 3.11 Å. The Au(3)-Au(5) bond length is 2.87 Å. Both Au(3)-Ge(1) bond lengths are 2.53 Å. In the fourth Au site, Au(4) is bonded in a 1-coordinate geometry to two equivalent Ca(2), three equivalent Ca(1), one Au(1), one Au(3), and one Ge(1) atom. The Au(4)-Ge(1) bond length is 2.47 Å. In the fifth Au site, Au(5) is bonded to four equivalent Ca(1), two equivalent Au(2), two equivalent Au(3), and four equivalent Au(1) atoms to form AuCa4Au8 cuboctahedra that share faces with two equivalent Au(5)Ca4Au8 cuboctahedra and faces with four equivalent Au(1)Ca4GeAu7 cuboctahedra. Ge(1) is bonded in a 8-coordinate geometry to three equivalent Ca(1), one Au(1), one Au(2), one Au(4), and two equivalent Au(3) atoms.