Thermal and magnetic properties of a low-temperature antiferromagnet Ce$_4$Pt$_{12}$Sn$_{25}$

We report specific heat ($C$) and magnetization ($M$) of single crystalline Ce$_4$Pt$_{12}$Sn$_{25}$ at temperature down to $\sim$\,50\,mK and in fields up to 3\,T. $C/T$ exhibits a sharp anomaly at 180\,mK, with a large $\Delta$$C$/$T$\,$\sim$\,30\,J/mol\,K$^2$-Ce, which, together with corresponding the cusp-like magnetization anomaly, indicate antiferromagnetic (AFM) ground state with N\'eel temperature $T_{\mathrm{N}}$\,=\,0.18\,K. Numerical calculations based on Heisenberg model reproduce both specific heat and magnetization data, and point to a very small Kondo scale $T_K$, clearly placing Ce$_4$Pt$_{12}$Sn$_{25}$ in the weak exchange coupling $J < J_c$ limit of the Doniac diagram. Magnetic field suppresses AFM state at $H^* \approx 0.7$ T. Anomalous behavior observed in $M$($H$) vs. $T$ for fields in the vicinity of $H^*$ points to a likely field-induced quantum critical point (QCP) at $H^*$.