Electronic states in a semimetal Ce ₃Sn ₇

We carried out the de Haas-van Alphen (dHvA) measurement and the pressure experiment of the electrical resistivity for an antiferromagnet Ce ₃Sn ₇ with the orthorhombic crystal structure. The detected dHvA branches are many in number and their dHvA frequencies are extremely small in magnitude, indicating that Ce ₃Sn ₇ is a semimetal. This is consistent with the result of the energy band calculations under the assumption that the 4f electrons of two Ce atoms in the 2(a) site are localized and the 4f electron of one Ce atom in the 4(i) site is itinerant. In the pressure experiment, the Néel temperature of T _N = 5.3 K is found to slightly increase with increasing pressure, becomes maximum around 1 GPa, then decreases steeply with further increasing pressure and most likely becomes zero between 3 and 4 GPa. The antiferromagnetic state is changed into the non-magnetic state under pressure.