Anisotropic magnetic phase diagram of the Kondo-lattice compound Ce3Pd20Ge6:: Observation of antiferromagnetic and quadrupolar ordering

From the measurement of the specific heat of single crystalline samples of Ce3Pd20Ge6, we have constructed magnetic phase diagrams for a magnetic field up to 4 T, which disclose a pronounced anisotropy along the three principal directions of [100], [110], and [111]. We have found that both the quadrupol and antiferromagnetic ordering temperatures exhibit distinct directional dependences on the external magnetic field and that new phase transitions evolve in the antiferromagnetic phase as well as in the ordered quadrupolar phase. These facts strongly suggest the existence of a complicated form of anisotropic interaction between the electric quadrupolar moment and the magnetic dipolar moment. The present result is briefly discussed in comparison with the reported one for CeB6.