  Entanglement measures constitute powerful tools in the quantitative
description of quantum many-body systems out of equilibrium. We study
entanglement in the current-carrying steady state of a paradigmatic
one-dimensional model of noninteracting fermions at zero temperature in the
presence of a scatterer. We show that disjoint intervals located on opposite
sides of the scatterer, and within similar distances from it, maintain
volume-law entanglement regardless of their separation, as measured by their
fermionic negativity and coherent information. The mutual information of the
intervals, which quantifies the total correlations between them, follows a
similar scaling. Interestingly, this scaling entails in particular that if the
position of one of the intervals is kept fixed, then the correlation measures
depend non-monotonically on the distance between the intervals. By deriving
exact expressions for the extensive terms of these quantities, we prove their
simple functional dependence on the scattering probabilities, and demonstrate
that the strong long-range entanglement is generated by the coherence between
the transmitted and reflected parts of propagating particles within the
bias-voltage window. The generality and simplicity of the model suggest that
this behavior should characterize a large class of nonequilibrium steady
states.
