  We review the evidence supporting valence-fluctuation mediated
superconductivity in CeCu2Si2 and CeCu2Ge2, where Tc reaches 2.4 K at high
pressure. In these systems the valence and magnetic critical points, at p_V and
p_c respectively, are well separated. Characteristic signatures associated with
both phenomena are distinct. In contrast, the valence and spin fluctuation
regions appear much closer in most Ce based compounds. Concerning d-transition
metals, superconductivity in pure iron emerges in the pressure window 15-30 GPa
with the onset of Tc up to almost 3 K. All relevant observations point to
unconventional superconductivity, likely mediated by ferromagnetic spin
fluctuations.
