High-field magnetoresistance and quantum effects in the organic compound (TMTSF)2PF6

The transverse magnetoresistance of (TMTSF) 2 PF 6 has been investigated in magnetic field up to 32 T, at low temperatures down to 4.2 K. Shubnikov-de Haas oscillations are directly observed on the magnetoresitance in fields higher than 18 T, but there is no evidence of a threshold field since the disappearance of oscillations can be explained by the normal field-dependent damping. However these oscillations vanish very quickly between 5 and 4.2 K. This unusual behaviour could be related to a phase-transition. Finally an exploration of the fundamental field versus θ is given (θ=angle between B and c * ), showing the warping of the «Fermi tubes» along the c * axis Etude experimentale de la magnetoresistance transverse dans des champs magnetiques allant jusqu'a 32 T, a basse temperature jusqu'a 4,2 K. Observation directe d'oscillations de Shubnikov-de Haas pour des champs superieurs a 18 T, sans qu'il soit certain qu'il existe un champ seuil, la disparition des oscillations pouvant s'expliquer par l'amortissement normal fonction du champ magnetique. Disparition rapide des oscillations entre 5 et 4,2 K, peut-etre due a une transition de phase. Exploration du champ fondamental en fonction de θ (angle entre B et axe c): gondolement des «tubes de Fermi» le long de c *