de Haas-van Alphen measurements made on the organic metal ${\beta }^{″}-(\mathrm{BEDT}-\mathrm{TTF}{)}_2{\mathrm{SF}}_5{\mathrm{CH}}_2{\mathrm{CF}}_2{\mathrm{SO}}_3$ reveal the existence of an ideal two-dimensional (2D) Fermi surface, but rather than having the conventional sawtooth wave form that is normally observed in all other 2D electron gases, instead, an “inverse sawtooth” wave form is observed, which is to be expected when the chemical potential is pinned at a constant value. While this proves the existence of the theoretically predicted quasi-one-dimensional band, it further implies that this band has an exceptionally large density of states.

• Received 28 October 1999

DOI:https://doi.org/10.1103/PhysRevB.61.7383