  We discuss, from a theoretical point of view, excitonic phases at the
pressure induced semiconductor-semimetal transition in $\rm
TmSe_{0.45}Te_{0.55}$,focusing, in particular, on the stability against an
electron-hole liquid. The electron-hole pair density parameter $r_s(E_g,T)$ is
calculated within the quasi-static plasmon pole approximation as a function of
temperature $T$ and energy gap $E_g$ and converted into $-E_g(r_s,T)$. A
comparison of this quantity, which is the electron-hole pair chemical
potential, with the exciton binding energy reveals that excitons should be
suppressed in contrast to experimental evidence for excitonic phases. We
suspect therefore inter-valley exciton scattering and exciton-phonon scattering
to substantially stabilise excitons in $\rm TmSe_{0.45}Te_{0.55}$.
