  We report specific heat ($C$) and magnetization ($M$) of single crystalline
Ce$_4$Pt$_{12}$Sn$_{25}$ at temperature down to $\sim$50mK and in fields up to
3T. $C/T$ exhibits a sharp anomaly at 180mK, with a large $\Delta
C/T\sim$30J/molK$^2$-Ce, which, together with the corresponding cusp-like
magnetization anomaly, indicates an antiferromagnetic (AFM) ground state with a
N\'eel temperature $T_N$=180mK. Numerical calculations based on a Heisenberg
model reproduce both zero-field $C$ and $M$ data, thus placing
Ce$_4$Pt$_{12}$Sn$_{25}$ in the weak exchange coupling $J<J_c$ limit of the
Doniach diagram, with a very small Kondo scale $T_K\ll T_N$. Magnetic field
suppresses the AFM state at $H^*\approx$0.7T, much more effectively than
expected from the Heisenberg model, indicating additional effects possibly due
to frustration or residual Kondo screening.
