De Haas-van Alphen oscillations in the 12 Å-methylene blue intercalation compound of 2H-TaS₂

We report on the first observation of de Haas-van Alphen oscillations in an organic intercalation compound of 2H-TaS₂. The 12 Å-methylene blue intercalation compound (12 Å-MB⁺-TaS₂) shows oscillations of the torque at magnetic fields higher than about 8 T. Four oscillation frequencies were observed at magentic fields of 110 T, 257 T, 368 T and 876 T. The effective masses of the three orbits with the highest frequencies are 1.0, 1.2 and 1.4 electron masses, respectively. A simple rigid-band model fails in interpreting these results.