Ultrahigh-resolution photoemission study of CePd3: absence of Kondo insulator gap

We have performed ultrahigh-resolution (DeltaE=8 meV) photoemission spectro scopy to examine the possibility of CePd3 being a 'Kondo insulator' as sugg ested by a recent optical measurement [Phys. Rev. B 53 (1996) R2948]. We fo und that the photoemission spectrum of CePd3 does not show any indication o f (pseudo) gap at E-F, differing from the well-established tempsrature-depe ndent (pseudo) Sap in Kondo insulators. The Ce 4f spectrum clearly shows th e 'Kondo resonance peak' at E-F, indicating the intrinsic metallic nature o f CePd3. These results strongly suggest that CePd3 is not a Kondo insulator but a conventional Kondo metal as suggested by thermodynamic measurements. (C) 2001 Elsevier Science B.V. All rights reserved.