1. a Commission of the European Communities, Joint Research Centre, Institute for the Tranuranium Elements , Postfach 2340, D-7500 , Karlsruhe , FRG
2. b Laboratoire Léon Brillouin, (C.E.A.-C.N.R.S.), C.E.N.Saclay , France
3. c Laboratoire de chimie-physique du solide, E.C.P. , Chatenay Malabry , France
4. e K.f.K. Karlsruhe, INFP, D-7500 Karlsruhe and Institut für Mineralogie , Lahnberge, D-3550 , Marburg , FRG
5. d K.f.K., I.H.Ch. , Postfach 3640, D-7500 , Karlsruhe , FRG