ULTRASOUND STUDIES OF U2ZN17 AND UCU5

We present here resonant ultrasound spectroscopy measurements of the e lastic moduli and attenuation for U2Zn17, and UCu5 through the respect ive T(N)'s of 9.7 and 15 K. For single-crystal U2Zn17, the data are th e first modulus measurements for this material, and exhibit a very lar ge softening of the sound velocity and an anomalous increase in attenu ation below T(N), while no precursors at all are observed above. Polyc rystalline UCu5, in contrast, exhibits weak softening above T(N), and a weak stiffening below.