  The asymmetric infinite-dimensional periodic Anderson model is examined with
a quantum Monte Carlo simulation. For small conduction band filling, we find a
severe reduction in the Kondo scale, compared to the impurity value, as well as
protracted spin screening consistent with some recent controversial
photoemission experiments. The Kondo screening drives a ferromagnetic
transition when the conduction band is quarter-filled and both the RKKY and
superexchange favor antiferromagnetism. We also find RKKY-driven ferromagnetic
and antiferromagnetic transitions.
