The magnetoresistance and magnetic torque of FeS are measured in magnetic fields $B$ of up to 18 T down to a temperature of 0.03 K. The superconducting transition temperature is found to be $T_c=4.1\mathrm{K}$, and the anisotropy ratio of the upper critical field $B_{c2}$ at $T_c$ is estimated from the initial slopes to be $\mathrm{\Gamma }\left(T_c\right)=6.9$. $B_{c2}\left(0\right)$ is estimated to be 2.2 and 0.36 T for $B\parallel ab$ and $c$, respectively. Quantum oscillations are observed in both the resistance and torque. Two frequencies $F=0.15$ and 0.20 kT are resolved and assigned to a quasi-two-dimensional Fermi surface cylinder. The carrier density and Sommerfeld coefficient associated with this cylinder are estimated to be $5.8\times {10}^{-3}$ carriers/Fe and $0.48\mathrm{mJ}/\left({\mathrm{K}}^2\mathrm{mol}\right)$, respectively. Other Fermi surface pockets still remain to be found. Band-structure calculations are performed and compared to the experimental results.

• Received 2 August 2016
• Revised 5 September 2016

DOI:https://doi.org/10.1103/PhysRevB.94.100503