DE HAAS-VAN-ALPHEN INVESTIGATIONS OF THE ORGANIC METAL ALPHA-(ET)(2)TLHG(SECN)(4)

We report on the first de Haas-van Alphen (dHvA) studies of the quasi- two-dimensional (2D) organic metal alpha-(ET)(2)TlHg(SeCN)(4). The ang ular dependence of the dHvA frequency and of the effective cyclotron m ass, m(c), follows perfectly the expected 2D 1/cos Theta behaviour. Th e angular dependence of the absolute amplitude of the dHvA oscillation s is in quantitative agreement with the Lifshitz-Kosevich behaviour. T hree distinct spin-splitting zeros can be observed. The extracted Valu e of g mu(b) is in accordance with a reduced electron-phonon coupling constant lambda(ep) in this non-superconducting material. Contrary to previous Shubnikov-de Haas results no field dependence of m(c) up to 2 9 T is observed.