  Iron-based superconductors, with the ThCr$_{2}$Si$_{2}$-type tetragonal
structure (122 family), due to the iron arsenide/selenide layers exhibit
several characteristic electronic properties. For example, multiband character
mosty associated with the $d$-orbitals of iron and the quasi-two-dimensional
(2D) cylindrical Fermi surface. Moreover, external hydrostatic pressure leads
to the isostructural phase transition from the tetragonal to
collapsed-tetragonal phase. In this paper, in relation to the iron-based
superconductors, we discuss the electronic properties of novel 122-family
member RbNi$_{2}$Se$_{2}$ [Liu H. et al., Phys. Rev. B 106, 094511 (2022)]. We
show that the two Fermi pockets exhibit quasi-2D character. Calculation of the
surface spectral function for the (001) surface shows that the surface states
are realized independently on the surface termination. Additionally, contrary
to the iron-based 122 compounds, RbNi$_{2}$Se$_{2}$ exhibits extraordinary
multiple isostructural phase transitions under pressure. Moreover, the Lifshizt
transition occurs under external pressure, which results into a strong
modification of the shapes of the Fermi pockets.
