In the case of RbBi2 𝜆 = 0.81 and 𝜔 𝑙𝑛 = 1.74 THz (equivalent to 83.5 K) leading to Tc = 3.23 K, reasonably close to the measured value 4.24 K. In case of CsBi2 EPC constant in larger (𝜆 = 0.92) leading to higher Tc = 3.85 K despite of lower logarithmic frequency. The estimated critical temperature is reasonably close to the experimental value Tc = 4.65 K. Both experimental and calculated values lead to a conclusion, that CsBi2 has higher critical temperature than RbBi2 due to slightly stronger electron-phonon coupling.