Ultrasonic attenuation measurements on LuBa/sub 2/Cu/sub 3/O/sub 7/ and HoBa/sub 2/Cu/sub 3/O/sub 7/

HoBa2Cu3O7 and LuBa2Cu3O7 show very different ultrasonic attenuation behavior at temperatures below 220 K. The Ho sample exhibits a broad maximum in attenuation at around 220 K, while the Lu sample shows a minimum followed by a plateau below 140 K. At Tc, the Ho sample shows a decrease in attenuation; there is no evidence for such a change in the Lu sample.