  Large-scale accretion shocks around massive clusters of galaxies, generically
expected in hierarchical scenarios of cosmological structure formation, are
shown to be potential sources of the observed ultrahigh energy cosmic rays
(UHECRs) by accelerating a mixture of heavy nuclei including the iron group
elements. Current observations can be explained if the source composition at
injection for the heavier nuclei is somewhat enhanced from simple expectations
for the accreting gas. The proposed picture should be testable by current and
upcoming facilities in the near future through characteristic features in the
UHECR spectrum, composition and anisotropy. The associated X-ray and gamma-ray
signatures are also briefly discussed.
