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JapanMagnetization, electrical resistivity and specific heat measurements were performed on highquality single crystalline SmTi 2 Al 20 (residual resistivity ratio ∼ 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 γ = 150 mJ/(K 2 mol). Specific heat analysis reveals that the ground state is a Γ 8 quartet state and the Sm magnetic dipole moment m Sm (∼ 0.5µ B at T ≃ 0) orders below T x in spite of the field-insensitive behavior. Possible reasons for the field insensitiveness will be discussed.The strongly correlated electron systems with caged structure (e.g. filled skutterudite RT 4 X 12 ) have attracted much attention because of the wide variety of interesting properties such as heavy fermion (HF) behavior, multipolar ordering, unconventional superconductivity (SC) and rattling motion of guest ions. In particular Pr-and Sm-based series have been intensively investigated due to unconventional physical properties ascribed to multipolar degrees of freedom in their low energy excitations, such as the unconventional HFSC in PrOs 4 Sb 12 , 1) a possible multipolar ordering in SmRu 4 P 12 2-4) and a field-insensitive HF state in SmOs 4 Sb 12 . 5) Among the cage structure compounds, RT 2 X 20 (R = rare earth, T = transition metal, X = Zn, Al) compounds crystallizing in the cubic CeCr 2 Al 20 -type structure with the space group Fd3m (#227) have attracted much attention recently. 6-10) In these compounds, R ion is surrounded by neighboring 16 X atoms and the symmetry at R site is a cubic point symmetry T d . 11-14) Recent studies on Al-based compounds clarified that PrT 2 Al 20 (T = Ti and V) show a HF behavior and a multipolar ordering attributed to the nonmagnetic Γ 3 ground state doublet. 15) On the other hand, there are little reports on Sm-based SmT 2 Al 20 although they are * E-mail address: higashin@tmu.ac.jp J. Phys. Soc. Jpn. LETTERS