The elastic constants of intermetallic compound PrNi5 with a hexagonal crys
tal structure have been investigated by the ultrasonic measurement. For the
present single crystal we have observed the elastic softening of C-44 belo
w 40 K. It is ascribed to the quadrupolar response for the crystalline elec
tric held state of PrNi5. (C) 1999 Elsevier Science B.V. All rights reserve
d.