Room temperature X-ray diffraction shows that Gd1-xNdxCu compounds crystall
ize either in the CsCl or in the FeB orthorhombic structure, which show dif
ferent magnetic properties. Thermal expansion measurements show that these
compounds undergo a structural transition, which takes place by a martensit
ic transformation. The existence of electronic states with different total
energy can explain the observed structural instability. (C) 1999 Elsevier S
cience B.V. All rights reserved.