We have determined the terahertz spectrum of the chiral langasite Ba\(_3\)NbFe\(_3\)Si\(_2\)O\(_{14}\) by means of synchrotron-radiation measurements. Two excitations are revealed that are shown to ...have a different nature. The first one, purely magnetic, is observed at low temperature in the magnetically ordered phase and is assigned to a magnon. The second one persits far into the paramagnetic phase and exhibits both an electric and a magnetic activity at slightly different energies. This magnetoelectric excitation is interpreted in terms of atomic rotations and requires a helical electric polarization.
