Unusual Field-Insensitive Phase Transition and Kondo Behavior in SmTi${}_2$Al${}_{20}$

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 ${\mathrm{\Gamma }}_8$ quartet state and the Sm magnetic dipole moment $m_{\mathrm{S}\mathrm{m}}$ ($\sim 0.5{\mu }_{\mathrm{B}}$ at $T\simeq$ 0) orders below $T_x$ in spite of the field-insensitive behavior. Possible reasons for the field insensitiveness will be discussed.