  We study the electromagnetic form factors of the doubly charmed baryons,
using covariant chiral perturbation theory within the extended on-mass-shell
(EOMS) scheme. Vector-meson contributions are also taken into account. We
present results for the baryon magnetic moments, charge and magnetic radii.
While some of the chiral Lagrangian parameters could be set to values
determined in previous works, the available lattice results for $\Xi_{cc}^+$
and $\Omega_{cc}^+$ only allow for robust constraints on the low-energy
constant (LEC) combination, $c_{89}(=-\frac{1}{3}c_8+4c_9)$. The couplings of
the doubly charmed baryons to the vector mesons have been estimated assuming
the Okubo--Zweig--Iizuka (OZI) rule. We also give the expressions for the form
factors of the double beauty baryons considering the masses predicted in the
framework of quark models. A comparison of our results with those obtained in
heavy baryon chiral perturbation theory (HBChPT) at the same chiral order is
made.
