STUDY OF STRUCTURAL ORDERING, KONDO EFFECTS AND MAGNETISM IN CEH2+X WITH 0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.65, THROUGH ELECTRICAL-RESISTIVITY MEASUREMENTS

Through electrical resistivity measurements on CeH2+x, we observe first, for x greater-than-or-equal-to 0.1, a structural order-disorder transition related to the excess hydrogen content x, which enters the octahedral interstitial sites. For x less-than-or-equal-to 0.34, we observe Kondo effects and correlated magnetic transitions at low temperatures, which are very sensitive to the hydrogen ordering. For x greater-than-or-equal-to 0.4, we observe a very strong increase of all resistivity terms, i.e. residual, magnetic and phonon contributions: it indicates that there is a change of the electronic structure involving a strong decrease of the conduction electron density; but it could also be due to a percolation problem with the coexistence of metallic and nearly insulating phases.