  Anomalies in the temperature dependences of the recoil-free factor, f, and
the average center shift, <CS>, measured by 57-Fe Mossbauer Spectroscopy, were
observed for the first time in the archetype of the \sigma-phase alloys system,
Fe-Cr. In both cases the anomaly started at the temperature close to the
magnetic ordering temperature, and in both cases it was indicative of lattice
vibrations hardening. As no magnetostrictive effects were found, the anomalies
seem to be entirely due to a spin-phonon coupling. The observed changes in f
and in <CS> were expressed in terms of the underlying changes in the potential,
\Delta E_p, and the kinetic energy, \Delta E_k, respectively. The former, with
the maximum value larger by a factor of six than the latter, decreases, while
the latter increases with T. The total mechanical energy change, \Delta E, was,
in general, not constant, as expected for the Debye-like vibrations, but it
resembled that of \Delta E_p. Only in the range of 4-15 K, \Delta E was hardly
dependent on T.
