  We study the out-of-equilibrium properties of the antiferromagnetic
Hamiltonian Mean-Field model at low energy. In this regime, the Hamiltonian
dynamics exhibits the presence of a stationary state where the rotators are
gathered in a bicluster. This state is not predicted by equilibrium statistical
mechanics in the microcanonical ensemble. Performing a low kinetic energy
approximation, we derive the explicit expression of the magnetization vector as
a function of time. We find that the latter displays coherent oscillations, and
we show numerically that the probability distribution for its phase is bimodal
or quadrimodal. We then look at the individual rotator dynamics as a motion in
an external time-dependent potential, given by the magnetization. This dynamics
exhibits two distinct time scales, with the fast one associated to the
oscillations of the global magnetization vector. Performing an average over the
fast oscillations, we derive an expression for the effective force acting on
the individual rotator. This force is always bimodal, and determines a low
frequency oscillation of the rotators. Our approach leads to a self-consistent
theory linking the time-dependence of the magnetization to the motion of the
rotators, providing a heuristic explanation for the formation of the bicluster.
