  Specific heat and transport measurements have revealed an unconventional
heavy-fermion (HF) state in SmOs4Sb12 single crystals. The electronic
specific-heat coefficient (gamma=0.82 J/K^2mol) and the coefficient (A) of the
quadratic temperature dependence of electrical resistivity are largely
enhanced, although the ratio A/gamma^2 is reduced from the Kadowaki-Woods ratio
of HF materials. Both gamma and A do not show any significant decrease in
applied field in contrast with Ce-based HF compounds, suggesting an
unconventional origin of the heavy quasiparticles. A weak ferromagnetic
ordering sets in below about 3 K, probably originating in the itinerant
quasiparticles.
