Investigations of the Fermi surface of a new organic metal: (BEDT-TTF)(4)[Ni(dto)(2)]

The Fermi surface (FS) of the new organic metal (BEDT-TTF)(4)[Ni(dto)(2)] h as been investigated by de Haas-van Alphen (dHvA) and Shubnikov-de Haas (Sd H) experiments. In both quantum oscillations with two different frequencies F-alpha = 634 T and F-beta = 4245 T are observed. These results confirm th e calculated FS, which consists of one-dimensional and two-dimensional part s separated by a small energy gap. It is shown that the temperature and fie ld dependence of the oscillation amplitudes can be well described by standa rd Lifshitz-Kosevich theory considering the magnetic breakdown by the so-ca lled coupled network model. Beatings of the oscillation amplitudes are obse rved by held-dependent dHvA and SdH experiments. They can be explained by a slightly warped FS showing that this material represents a quasi-two-dimen sional electronic system. The observed beating nodes in the dHvA and SdH si gnals appear at different magnetic fields. This fact is discussed in terms of additional scattering mechanisms.