  We argue that the stable (color singlet) supermassive gravitinos proposed in
our previous work can serve as seeds for giant primordial black holes. These
seeds are hypothesized to start out as tightly bound states of fractionally
charged gravitinos in the radiation dominated era, whose formation is supported
by the universally attractive combination of gravitational and electric forces
between the gravitinos and anti-gravitinos (reflecting their `almost BPS-like'
nature). When lumps of such bound states coalesce and undergo gravitational
collapse, the resulting mini-black holes can escape Hawking evaporation if the
radiation temperature exceeds the Hawking temperature. Subsequently the black
holes evolve according to an exact solution of Einstein's equations, to emerge
as macroscopic black holes in the transition to the matter dominated era, with
masses on the order of the solar mass or larger. The presence of these seeds at
such an early time provides ample time for further accretion of matter and
radiation, and would imply the existence of black holes of almost any size in
the universe, up to the observed maximum.
