Specific heat is one of the most fundamental thermodynamic quantities. The measurements at very low temperatures are particularly important for the studies of exotic phenomena found in
correlated systems, such as non-Fermi liquid behavior, unconventional superconductivity and quantum spin liquid.
However, at very low temperatures, specific heat measurements become difficult because of glowing thermal boundary resistances and so on. In our recently published paper, we presented the detailed introduction of our relaxation calorimetry designed for tiny samples down to very low temperatures of 0.03 K. Especially, we discussed how to analyze the relaxation curves which are modified by an internal thermal relaxation in the sample or in the sample stage of the specific heat cell.  As an example, we discussed the measurements performed for a-YbAlB4 in a magnetic field of 5 T, where we found the triple exponential decay due to a thermal relaxation between electron and nuclear contributions at relatively high temperature well above 0.1 K. Our modified analysis provides the best solution in such a case. 

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​For the detail, see Y. Matsumoto and S. Nakatsuji, RSI 89, 033908 (2018). This work was selected as a Editor's Picks.