The electron structure of metallic layers in the quasi-two-dimensional dual-layered organic metal (BETS)$_{4}$HgBr$_{4}$(C$_{6}$H$_{4}$Cl$_{2}$)

We have studied the behavior of the Shubnikov–de Haas (SdH) oscillations in the quasi-two-dimensional dual-layered organic metal (BETS)$_{4}$HgBr$_{4}$(C$_{6}$H$_{4}$Cl$_{2}$). It is established that the spectrum of SdH oscillations in this compound agrees well with theoretical calculations and qualitatively coincides with the analogous spectrum of (ET)$_{4}$HgBr$_{4}$(C$_{6}$H$_{4}$Cl$_{2}$) isostructural organic metal. The fractional substitution of sulfur by selenium in the cationic layer strongly decreases the values of cyclotron masses. This decrease is most probably caused by weakening of the electron–phonon interaction.