Abstract

Tight-binding band structure calculations as well as magnetoresistance and magnetization measurements were carried out in order to characterize the Fermi surface of the novel organic metal (BEDO-TTF)₅[CsHg(SCN)₄]₂. The tight-binding calculations suggest that the Fermi surface can be described as containing two contributions: a closed two-dimensional portion associated with holes and an open pseudo-one-dimensional portion associated with electrons. Shubnikov-de Haas and de Haas-van Alphen oscillations were observed in magnetic fields of up to 14 T and temperatures of 1.5–4.2 K. Four frequencies (F₁ = 650 T, F₂ = 2600 T, F₃ = 3200 T and F₄ = 3850 T) associated with the Shubnikov-de Haas oscillations were found. The F₁ and F₄ frequencies are in good agreement with the calculated Fermi surface provided that the possibility of a magnetic breakdown effect is taken into account. It is also suggested that the F₂ and F₃ frequencies can be understood in the frame of the quantum interference effect.