  A new quaternary intermetallic borocarbide TmCo2B2C has been synthesized via
a rapid-quench of an arc-melted ingot. Elemental and powder-diffraction
analyses established its correct stoichiometry and single-phase character. The
crystal structure is isomorphous to that of TmNi2B2C(I4/mmm) and is stable over
the studied temperature range. Above 7 K, the paramagnetic state follows the
modified Curie-Weiss behavior (X=C/(T-theta)+X0 wherein X0=0.008(1) emu/mole
and the temperature-dependent term reflecting the paramagnetism of the Tm
subsystem: ueff=7.6(2) uB [in agreement with the expected value for a free Tm3+
ion] and theta = -4.5(3) K. Long range ferromagnetic order of the Tm sublattice
is observed to develop around ~1 K. No superconductivity is detected in
TmCo2B2C down to 20 mK, a feature which is consistent with the general trend in
the RCo2B2C series. Finally, the influence of the rapid-quench process on the
magnetism (and superconductivity) of TmNi2B2C will be discussed and compared to
that of TmCo2B2C.
