Interlayer magnetoresistance of the quasi-two-dimensional organic superconductor ${\beta }^{″}-(\mathrm{BEDT}-\mathrm{TTF}{)}_4({\mathrm{NH}}_4\left)\right[\mathrm{Fe}\left({\mathrm{C}}_2{\mathrm{O}}_4{)}_3\right]\cdot \mathrm{DMF}$ has been investigated in pulsed magnetic fields of up to 55 T in the temperature range from 1.6 K to 4.2 K. According to band-structure calculations, the Fermi surface of this compound originates from hybridized intersecting hole tubes with a cross sectional area equal to the first Brillouin-zone (FBZ) area, leading to two compensated electron and hole orbits. Actually, the Fourier spectrum of the oscillatory magnetoresistance exhibits various frequencies which can be regarded as linear combinations of the two frequencies with the highest amplitude $[F_a=(48\mathrm{}\pm 2)T$ and $F_b=(241\mathrm{}\pm 5)T]$ corresponding to 1.2% and 6.0% of the FBZ area, respectively. The oscillatory spectrum can be accounted for by three compensated electron and hole orbits and combination frequencies typical of networks of orbits coupled by magnetic breakthrough.

• Received 16 May 2003

DOI:https://doi.org/10.1103/PhysRevB.69.144523