  We report the first observation of new lines in the infrared spectrum of a
crystal due to unit-cell doubling at the spin-Peierls transition (in NaV_2O_5).
The change in the shape of the spectral lines at the spin-Peierls transition is
recorded for the first time. A contour characteristic of a Fano resonance is
observed above the transition temperature Tsp and the standard symmetric
contour is observed below Tsp. We attribute this effect to the opening of a gap
in the magnetic-excitation spectrum at the spin-Peierls transition.
