  We investigate the dissociation of $H_2^+$ into a proton and a $H^0$ after
single ionization with photons of an energy close to the threshold. We find
that the $p^+$ and the $H^0$ do not emerge symmetrically in case of the $H_2^+$
dissociating along the $1s\sigma_g$ ground state. Instead, a preference for the
ejection of the $p^+$ in the direction of the escaping photoelectron can be
observed. This symmetry breaking is strongest for very small electron energies.
Our experiment is consistent with a recent prediction by Serov and Kheifets
[Phys. Rev. A 89, 031402 (2014)]. In their model, which treats the
photoelectron classically, the symmetry breaking is induced by the retroaction
of the long range Coulomb potential onto the dissociating $H_2^+$.
