  We investigate the paramagnetic periodic Anderson model using the dynamical
mean-field theory in combination with the modified perturbation theory which
interpolates between the weak and strong coupling limits. For the symmetric
PAM, the ground state is always a singlet state. However, as function of the
hybridization strength, a crossover from collective to local Kondo screening is
found. Reducing the number of conduction electrons, the local Kondo singlets
remain stable. The unpaired f-electrons dominate the physics of the system. For
very low conduction electron densities, a large increase of the effective mass
of the quasiparticles is visible, which is interpreted as the approach of the
Mott-Hubbard transition.
