Tunneling spectra of NbSe3 in magnetic fields

The charge density wave gaps of NbSe3 have been carefully determinated by t unneling spectroscopy. In contrast to earlier work, the gap parameter assoc iated with the 59 K transition obtained in the present measurements is very close to the mean field value. The gap structures for both the 145 K and 5 9 K transitions are found to be essentially independent of the applied magn etic field H. The present findings strongly suggest that the anomalous magn etotransport properties of the material originate from some other mechanism than a X-induced improvement of Fermi surface nesting.