The lattice constants, a and c, are reported for the alloys, PrNi2Si2
and GdNi2Si2 in the temperature interval 12-300K. The c parameter for
PrNi2Si2 exhibits a distinct drop at 60K indicating the existence of a
lattice strain. There is no observable anomaly at 60K in the heat-cap
acity and electrical resistivity. We attribute this lattice strain to
4f electric quadrupolar effects.