Thermoelectric study of the phase transitions in cerium at ultrahigh pressures from $0$ to $20$ GPa

The pressure dependences of the thermoelectric power $S$ of Ce samples were measured at pressures $P$ from $0$ to $20$ GPa in a synthetic diamond cell. The dependence of $S$ on $P$ was found to be nonmonotonic both in the region of transitions from the fcc ($\gamma$) phase to the modified fcc ($\alpha$) phase followed by the transition to the body-centered monoclinic ($\alpha''$) and the tetragonal ($\varepsilon$) phases at pressures of about $1$, $5$–$6$, and $12$–$15$ GPa, respectively, and in the stability region of these phases. The thermoelectric power sign was found to be positive for all high-pressure Ce phases. The found $S$ ($P$) dependence was compared with the published computational data on the electronic structure of the cerium phases. Cerium was taken as an example to demonstrate the advantage of the thermoelectric studies over other methods of investigation of phase transitions.