We have measured the upper critical magnetic field, lower critical magnetic
held, and low-temperature specific heat of LuNi2B2C. Our upper critical-fi
eld measurements above similar to2 K are consistent with earlier measuremen
ts by other groups. The upper critical field exhibits a finite slope as T--
>0, and we discuss possible origins of this very unusual behavior. We obser
ve a linear temperature dependence for the lower critical field of our sing
le-crystal sample, a temperature dependence that disagrees with earlier mea
surements on polycrystals and suggests that the lower critical field may be
anisotropic. The Sommerfeld coefficient increases with magnetic field as H
-epsilon with epsilon = 0.63 +/- 0.12 in qualitative agreement with earlier
work. The temperature dependence of the zero-field electronic specific hea
t is exponential well below T-c. We discuss our results in light of recent
proposals of both anisotropic s-wave and d-wave superconductivity for LuNi2
B2C. Our data seem most consistent with strong-coupling superconductivity a
nd a weakly anisotropic s-wave energy gap.