Magnetization, electrical resistivity and specific heat measurements were performed on high-quality single crystalline SmTi$_2$Al$_{ 20}$ (residual resistivity ratio $\sim$ 40) grown by Al self-flux method. A Kondo-like $\log T$ dependence in the resistivity is observed below 50 K. We discovered a field-insensitive phase transition at $T_{ x}$ = 6.5 K and a field-insensitive heavy fermion behavior with the electronic specific heat coefficient $\gamma$ = 150 mJ/(K$^{ 2}$ mol). Specific heat analysis reveals that the ground state is a $\Gamma_{ 8}$ quartet state and the Sm magnetic dipole moment $m_{ { \rm Sm}}$ ($\sim 0.5 \mu_{ { \rm B}}$ at $T \simeq$ 0) orders below $T_{ x}$ in spite of the field-insensitive behavior. Possible reasons for the field insensitiveness will be discussed.
Categories: cond-mat.str-el