data_BaAl2Tl
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.7
_cell_length_b   5.7
_cell_length_c   5.7
_cell_angle_alpha   126.88
_cell_angle_beta   126.88
_cell_angle_gamma   78.45
_symmetry_Int_Tables_number   1
_chemical_formula_structural   BaAl2Tl
_chemical_formula_sum   'Ba1 Al2 Tl1'
_cell_volume   114.62
_cell_formula_units_Z   1
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ba  Ba2  1  0.0  0.0  0.0  1.0
  Al  Al0  1  0.0  0.55  0.21  1.0
  Al  Al1  1  0.55  0.0  0.21  1.0
  Tl  Tl3  1  0.0  0.0  0.41  1.0

data_BaAl2Tl
_symmetry_space_group_name_H-M   Cm
_cell_length_a   7.21
_cell_length_b   7.21
_cell_length_c   5.7
_cell_angle_alpha   90.0
_cell_angle_beta   129.22
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   BaAl2Tl
_chemical_formula_sum   'Ba2 Al4 Tl2'
_cell_volume   229.25
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ba  Ba0  2  0.0  0.0  0.0  1.0
  Al  Al1  4  0.07  0.27  0.34  1.0
  Tl  Tl2  2  0.09  0.5  0.59  1.0

Ba Al Al Tl
BaTlAl2 crystallizes in the monoclinic Cm space group. Ba(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Tl(1) and two equivalent Al(1) atoms. There is one shorter (2.36 Å) and one longer (3.34 Å) Ba(1)-Tl(1) bond length. Both Ba(1)-Al(1) bond lengths are 2.59 Å. Tl(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1) and two equivalent Al(1) atoms. Both Tl(1)-Al(1) bond lengths are 2.09 Å. Al(1) is bonded in a distorted linear geometry to one Ba(1) and one Tl(1) atom.