  An explanation is given for the observed magnetic-field dependence of the
low-temperature specific heat coefficient of Yb(4)As(3). It is based on a
recently developed model for that material which can explain the observed
heavy-fermion behaviour. According to it the Yb(3+)-ions are positioned in a
net of parallel chains with an effective spin coupling of the order of J = 25
K. The magnetic-field dependence can be understood by including a weak magnetic
coupling J' between adjacent chains. The data require a ratio J'/J of about
10^{-4}. In that case the experimental results can be reproduced very well by
the theory.
