De Haas-Van Alphen experiments under extreme conditions of low temperature, high field and high pressure, for high-quality cerium and uranium compounds

When pressure is applied to cerium and uranium compounds, the magnetic ordering temperature is suppressed and becomes zero at a critical pressure P_c. Around P_c, non-Fermi liquid and/or superconductivity are observed. We clarified a change of the electronic state via a de Haas-van Alphen (dHvA) experiment when pressure crosses P_c. The dHvA experiment under pressure was done for the antiferromagnets CeRh₂Si₂ and CeRhIn₅, and for a ferromagnet UGe₂. We found an abrupt change of the Fermi surface for CeRh₂Si₂ and UGe2 when crossing P_c, indicating a first-order like phase transition. For CeRhIn₅, the topology of the Fermi surface was unchanged, but the cyclotron mass increased steeply above 1.6 Gpa, where superconductivity sets in.