Quantum oscillations in the magnetoresistance and susceptibility of $2H$-Ta${\mathrm{S}}_2$ have been used to determine Fermi-surface cross sections. Eleven frequencies in the range from 0.04 to 6.44 MG have been observed corresponding to sections arising from the charge-density-wave transition at 75 K. Comparison to the frequencies observed in $4Hb$-Ta${\mathrm{S}}_2$ shows that the Fermi-surface cross sections are similar in both the $2H$ and $4Hb$ phases indicating relatively little charge transfer between octahedral and trigonal prismatic layers in $4Hb$-Ta${\mathrm{S}}_2$. The angular dependence observed for a number of sections in $2H$-Ta${\mathrm{S}}_2$ shows a $sec\theta$ dependence characteristic of cylinders while others show a more three-dimensional behavior in contrast to $4Hb$-Ta${\mathrm{S}}_2$ where all of the lowest frequencies show a $sec\theta$ dependence. Comparison to results on $2H$-Ta${\mathrm{Se}}_2$ and to band-structure calculations and band-folding models will also be made.

• Received 9 May 1978

DOI:https://doi.org/10.1103/PhysRevB.18.3790