OBSERVATION OF A HIGH-FIELD ANOMALY IN THE LOW-TEMPERATURE SPECIFIC-HEAT OF CECU2SI2

We have performed high-magnetic-field, to 16 T, low-temperature specific-heat measurements for CeCu2.2Si2, CeCu2Si2, and CeCu1.9Si2. The first two materials, which are superconducting, exhibit a pronounced structure in C/T at T is similar to 0.6 K and H greater-than-or-equal 10 T. Changing the field from 10 to 16 T does not affect the anomaly. The nonsuperconducting, CeCu1.9Si2, sample does not exhibit a similar anomaly in the investigated temperature range, 0.32-1 K. Possible correlations between this structure and the low-temperature, high-field phase diagram of CeCu2Si2 are discussed.