title: X-ray resonant scattering study of the quadrupolar order in UPd3.
abstract: Quadrupolar ordering in a 5f electron system has been observed directly for the first time, using x-ray scattering techniques. In UPd (3) at low temperatures satellite peaks appear at (1,0,l) (orthorhombic notation) with l odd and even. Both sets of peaks show a resonant enhancement of the scattering at the M(IV) edge of U. At resonance, the dominant scattering of the l odd peaks occurs in the unrotated polarization channel, whereas for l even a significant rotated component is found. These results are discussed in terms of possible structures of the antiferroquadrupolar phases.
authors.affiliation: Materials Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark.
authors.forename: D F
authors.initials: DF
authors.lastname: McMorrow
authors.forename: K A
authors.initials: KA
authors.lastname: McEwen
authors.forename: U
authors.initials: U
authors.lastname: Steigenberger
authors.forename: H M
authors.initials: HM
authors.lastname: Rønnow
authors.forename: F
authors.initials: F
authors.lastname: Yakhou