Measurements of electrical resistance under high pressure and neutron diffr
action in high-magnetic field of single crystalline UNi2Si2 have been perfo
rmed. We have found the analogy between the p-T and B-T magnetic phase diag
rams. It is also found that the propagation vector qz of incommensurate ant
iferromagnetic phase decreases with increasing magnetic field. A new pronou
nced pressure-induced incommensurate-commensurate magnetic phase transition
has been detected. (C) 2001 Elsevier Science B.V. All rights reserved.