Thermoelectric power of linear chain mercury compounds

Linear-chain mercury compounds were investigated by measuring the thermoelectric power of ${\mathrm{Hg}}_{2.86}$As${\mathrm{F}}_6$ in the temperature range $4.2\le T\le 300$ K. The temperature dependence of the thermoelectric power above 100 K along the isotropic $\hat{a}$ and $\hat{b}$ axes exhibits a linear, negative slope indicating that electrons are the majority carriers along the mercury chains and a Fermi energy of 4.2±0.5 eV. Along the $\hat{c}$ axis, the temperature dependence of the thermoelectric power above 100 K exhibits a positive slope indicating hole-dominated conduction. A large, positive thermoelectric power peak at 13±3 K along both principal directions is considered to be due to phonon drag, which points to a relatively low Debye temperature comparable to that of elemental mercury. A phase transition between 180 and 200 K is evident in the $c$-axis data.