AMRO measurements on the organic conductor (BEDT-TTF) ₄ [ Ni(dto)₂

Abstract
The charge-transfer salt [ (BEDT-TTF) ₄] ²⁺[ Ni(dto) ₂] ^2- is a quasi two-dimensional organic metal [1]. This is confirmed by the resistivity ratio / at 300K, where (a,b) represents the high conducting plane. The material shows strong quantum oscillations (QOs) above about 1.2T (at 20mK) with two QO frequencies F T and F =4245T. We report on AMRO (angular dependent magneto-resistance oscillation) measurements on this material, which were performed by rotating single crystals around different axes within the (a,b) plane at different fixed fields (up to 13T). The results confirm the size and also approximately the shape of the slightly warped lens-shaped orbit obtained by the band structure calculations as well as Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) measurements. In addition a strong sharp magneto-resistance peak was found at 90° (i.e., B//(a,b) plane), which hints to coherent interlayer carrier transport [3]. In the vicinity of this peak further anomalies were observed, which may be oscillations reported by Danner et al. caused by a warped one dimensional band [4]. Key words. Organic metal - AMRO - quasi two-dimensional electronic system - coherent interlayer transport.