  Precision measurements of free neutron $\beta$-decay have been used to
precisely constrain our understanding of the weak interaction. However the
neutron Fierz interference term $b_n$, which is particularly sensitive to
Beyond-Standard-Model tensor currents at the TeV scale, has thus far eluded
measurement. Here we report the first direct constraints on this term, finding
$b_n = 0.067 \pm 0.005_{\text{stat}} {}^{+0.090}_{- 0.061}{}_{\text{sys}}$,
consistent with the Standard Model. The uncertainty is dominated by absolute
energy reconstruction and the linearity of the beta spectrometer energy
response.
