The symmetry problem in alpha '-NaV2O5

We discuss the symmetry of alpha'-NaV2O5 in the high temperature phase on t he basis of optical conductivity data. Conclusive information cannot be obt ained by studying the optically allowed lattice vibrations. However, intens ity and polarization of the electronic excitations give a direct indication for a broken-parity electronic ground-state. This is responsible for the d etection of charged bi-magnons in the optical spectrum. (C) 1999 Elsevier S cience B.V. All rights reserved.