Figure shows the Fermi surface (FS) of RbBi2 and CsBi2 calculated with and without SOC. Since the differences in FS between the two compounds are negligible, we will discuss the RbBi2 case only. The only difference between the two compounds lies in the Fermi velocity which is slightly smaller in the case of CsBi2 in the [1 0 0] direction. This is consistent with a less dispersed character of bands around EF and a higher DOS at the Fermi level of this compound. In the scalar relativistic case there are four bands per spin crossing the EF, and thus four FS branches. First one has a dodecahedral shape with almost completely flat faces. It is similar to the Fermi surface of Polonium which was concluded to lead to strong nesting, as one q-vector (connecting two flat faces) is able to connect many points of these faces of the Fermi surface, leading to the Kohn anomaly in phonon spectrum . The hybridization causes the presence of cone-like corners, which at E = 0.35 eV below the EF are visible as Dirac-like bands at the L point. Additionally, there are small pockets around K and U points. This part of Fermi surface is associated with the band which is approximately parabolic around the Γ point and is contributing to Dirac-like cones at other points.