The degeneracy of bands at X-point is symmetry-enforced and leads RbBi2 and CsBi2 to be classified topologically as ESFD (enforced semimetals with Fermi degeneracy), i.e. it is a material, which could be driven to a topological insulator state by symmetry breaking . In contrast to the behavior at the X point, at L the bands are not only shifted (one of them is shifted above the Fermi level), but also split. flat, resulting in a peak in the phonon DOS. The exception is the highest mode, which is the breathing mode of a pyrochlore network associated with a movement of Bi atoms toward the center of the tetrahedron and breaking of the inversion symmetry of the lattice (see Fig. (e)).