Single crystals of a Tb0.4Y0.6Ni2B2C intermetallic compound, which exhibit the coexistence of superconductivity and low-temperature magnetic ordering, have been grown by vertical floating-zone melting. The growth process of these intermetallic compound crystals is analysed from in situ tracking of the zone temperature, segregation behaviour along the axis, and the constitution of the ultimate zone. The slight shift of composition along the crystal axis, increase in Tb/(Tb + Y)-fraction but decrease in Ni/B ratio, were revealed by electron probe microanalysis. The superconducting transition temperature along the axis co-ordinate is nearly constant at T-c = 4.0 +/- 0.1 K with a transition range of Delta T-c = 0.8 K. Stacking faults resulting from a local deviation of the stoichiometric composition were found near the end of the crystal by TEM investigations.