Galvanomagnetic Effects in the Charge-Density-Wave State of 2H-NbSe2and 2H-TaSe2

The magnetoresistance and Hall coefficient in the charge-density-wave (CDW) state of 2 H -NbSe 2 and 2 H -TaSe 2 have been measured at low temperatures in magnetic fields up to 150 kOe, using high-quality single crystals. The results on these two compounds have been compared with those on 2 H -NbS 2 which has no CDW transition. By the comparison, several anomalous features in the CDW systems (2 H -NbSe 2 and -TaSe 2 ) have been made clear: 1) The magnetoresistance is relatively large and exhibits a linear dependence on magnetic field. 2) The Hall coefficient shows a strong field dependence including a minimum. We consider that the observed behaviors in the CDW systems may be explained by reconstruction of the Fermi surface in the CDW state and magnetic breakdown through the CDW gaps,