[en] Highlights: • The aromaticity of all-metal clusters is investigated. • The magnetically-induced current density is calculated in a four-component relativistic formulation. • The relativistic effects on ring current strengths is investigated. • The spin-orbit interaction plays a significant role in aromaticity of heavy-atom systems. We report about the spin-orbit effects on the aromaticity of the ${\mathrm{B}}_4^{2-}\text{,}{\mathrm{Al}}_4^{2-}\text{,}{\mathrm{Ga}}_4^{2-}$, ${\mathrm{In}}_4^{2-}$ and ${\mathrm{Tl}}_4^{2-}$ clusters via the magnetically-induced current density method. All-electron density functional theory (DFT) calculations were carried out using the four-component Dirac-Coulomb (DC) Hamiltonian, including scalar and spin-orbit relativistic effects. The relativistic values for ring current strengths were obtained by numerical integration over the current flow. These values were compared to the scalar relativistic and non-relativistic values, in order to assess the corresponding contributions to aromaticity. It was found that in the heavy cluster, ${\mathrm{Tl}}_4^{2-}$, there is a significant influence of both scalar and spin-orbit relativistic effects.