Tm 4 B 3 C 4 crystallizes in the triclinic Gd 4 B 3 C 4 structure type, space group P1¯ , a=3.4850(2), b=3.5220(2), c=11.6972(6), α=92.86(1), β=96.43(1), γ=90.14(1) according to X-ray powder diffraction. The magnetic properties of the compound Tm 4 B 3 C 4 have been measured in the temperature range 2K<T<300K and in various external fields up to B=7T. The sample undergoes an anti-ferromagnetic transition at T N =3K, and in fields B>0.1T a meta-magnetic transition is encountered. The measurements of the temperature dependence of the electrical resistivity proves a poor metallic state of this compound.