The ternary compound UNiAl, crystallizing in the ZrNiAl-type structure
, is an itinerant antiferromagnet with magnetic moments of less than 0
.8mu(B) per U atom and with a high gamma value of 164 mJ/mol K2. The a
nisotropic response of the electronic properties to magnetic field is
closely connected with the huge uniaxial magnetic anisotropy, observed
not only in the magnetically ordered state, but also in the paramagne
tic region. The origin of this anisotropy can be found in a strongly a
nisotropic hybridization. The magnetic ordering temperature, T(N) = 19
.3 K, is reduced upon applying the field along the c axis of the hexag
onal structure, which is the easy-magnetization direction. Antiferroma
gnetic ordering is suppressed by magnetic fields higher than the criti
cal field of the metamagnetic transition, which is 11.35 T at 1.4 K. T
he electronic contribution to the specific heat is gradually enhanced
by the magnetic field up to the transition, where a gamma value of abo
ut 260 mJ/mol K2 is recorded. In higher fields, the gamma coefficient
is gradually suppressed even below the zero-field value and reaches 14
3 mJ/mol K2 at 20 T. The magnetic field applied in the basal plane has
a negligible effect on both T(N) and gamma. The pronounced anisotropy
is also found in the low-temperature electrical resistivity, which is
considerably reduced in fields above the metamagnetic transition. Str
ong indications of anisotropic magnetic fluctuations can be traced in
a number of experimental findings on pure UNiAl and also on Y-, Co-, o
r Fe-substituted samples, in which a fast decay of magnetic ordering i
s observed.