We report a systematic study of the intermetallic compound DyNi2B2C, w
ith variations in the starting compositions of C and Dy. Our results s
how that for an exact starting composition of 1:2:2:1, the compound fo
rms without any impurity phases and a superconducting transition with
an onset as high as 6 K is observed. Excess of C or Dy in the compound
is found to be detrimental to the superconducting properties.