  We have measured the electrical resistivity of cerium monochalcogenices, CeS,
CeSe, and CeTe, under high pressures up to 8 GPa. Pressure dependences of the
antiferromagnetic ordering temperature $T_{N}$, crystal field splitting, and
the $\ln T$ anomaly of the Kondo effect have been studied to cover the whole
region from the magnetic ordering regime at low pressure to the Fermi liquid
regime at high pressure. $T_{N}$ initially increases with increasing pressure,
and starts to decrease at high pressure as expected from the Doniach's diagram.
Simultaneously, the $\ln T$ behavior in the resistivity is enhanced, indicating
the enhancement of the Kondo effect by pressure. It is also characteristic in
CeX$_{c}$ that the crystal field splitting rapidly decreases at a common rate
of $-12.2$ K/GPa. This leads to the increase in the degeneracy of the $f$ state
and further enhancement of the Kondo effect. It is shown that the pressure
dependent degeneracy of the $f$ state is a key factor to understand the
pressure dependence of $T_{N}$, Kondo effect, magnetoresistance, and the peak
structure in the temperature dependence of resistivity.

Strongly Correlated Electrons