Symmetry of crystals composed of two Bravais sublattices in 6D crystal spaces

It is shown that the symmetry of crystals composed of two Bravais sublattices can be determined in 6D spaces, which are two orthogonal 3D subspaces. Twenty one sets in 6D space satisfy this requirement. The Bravais classes in these sets and the conditions of translation compatibility of orthogonal 3D subspaces are discussed. A consideration of the subordination scheme for systems leaves only 19 significant sets. Crystals with a fluorite lattice, in which the cation sublattice has the translational symmetry of the crystal, and crystals with a cuprite lattice, in which the anion and cation sublattices have different translational symmetries, are considered as an illustration.