  We report the results of magnetic, heat-capacity, electrical and
magnetoresistance measurements on Ho4RhAl and Er4RhAl, characterized by 3 sites
for rare-earths (R). Antiferromagnetic ordering sets in at (T_N =) about 8.8
and 4.0 K respectively. While Ho compound appears to enter into a complex
spin-glass phase at T less thanT_N (at nearly 5 K), spin-glass component
appears to set in essentially almost at T_N for the Er case. The loss of the
spin-disorder contribution in the magnetically ordered state is not pronounced,
mimicking that in Gd2PdSi3, a compound which now attracts interest in the area
of topological Hall effect and magnetic skyrmions, indicating complex Fermi
surface. There is a minimum in the temperature dependence of electrical
resistivity in the case of only Ho above T_N, but significant negative
magnetoresistance is observed over a wide temperature range in the paramagnetic
state increasing with decreasing temperature for both the cases. This finding
establishes that these compounds belong to a select group of intermetallics in
which spin-disorder contribution apparently increases gradually as one
approaches respective TN with decreasing temperature. This could be an
experimental signature for the effect due to classical spin-liquid above T_N.
In view of these properties analogous to those of Gd2PdSi3, it is of interest
to investigate these 4:1:1 compounds further to understand possible
unconventional roles of itinerant electrons, not only in the magnetically
ordered state but also in the paramagnetic state, predicted by some theories in
recent years for which this Gd compound is considered to be a classic
example.Besides, magnetoresistance and isothermal entropy change
(magnetocaloric effect) track each other.
