The low-temperature electronic state of the layered organic charge-transfer salt $\kappa -{\left(\mathrm{BETS}\right)}_2{\mathrm{FeCl}}_4$ was probed by interlayer electrical resistance measurements under magnetic field. Both above and below $T_{\mathrm{N}}=0.47$ K, the temperature of antiferromagnetic ordering of $3d$-electron spins of ${\mathrm{Fe}}^{3+}$ localized in the insulating anion layers, a nonsaturating linear $R\left(T\right)$ dependence has been observed. A weak superconducting signal has been detected in the antiferromagnetic state, at temperatures $\le 0.2$ K. Despite the very high crystal quality, only a tiny fraction of the sample appears to be superconducting. Aside from a small kink feature in the resistivity, the impact of the antiferromagnetic ordering of localized ${\mathrm{Fe}}^{3+}$ spins on the conduction $\pi$-electron system is clearly manifested in the Fermi surface reconstruction, as evidenced by Shubnikov–de Haas oscillations. The “magnetic-field–temperature” phase diagrams for the field directions parallel to each of the three principal crystal axes have been determined. For magnetic field along the easy axis, a spin-flop transition has been found. Similarities and differences between the present material and the sister compound $\kappa -{\left(\mathrm{BETS}\right)}_2{\mathrm{FeBr}}_4$ are discussed.

• Received 14 July 2016

DOI:https://doi.org/10.1103/PhysRevB.94.205104