  In experiments, the ternary Eu pnictide EuRh2P2 shows an unusual coexistence
of a non-integral Eu valence of about 2.2 and a rather high Neel temperature of
50 K. In this paper, we present a model which explains the non-integral Eu
valence via covalent bonding of the Eu 4f-orbitals to P2 molecular orbitals. In
contrast to intermediate valence models where the hybridization with
delocalized conduction band electrons is known to suppress magnetic ordering
temperatures to at most a few Kelvin, covalent hybridization to the localized
P2 orbitals avoids this suppression. Using perturbation theory we calculate the
valence, the high temperature susceptibility, the Eu single-ion anisotropy and
the superexchange couplings of nearest and next-nearest neighbouring Eu ions.
The model predicts a tetragonal anisotropy of the Curie constants. We suggest
an experimental investigation of this anisotropy using single crystals. From
experimental values of the valence and the two Curie constants, the three free
parameters of our model can be determined.
