  Observations across many families of unconventional materials motivative the
search for robust mechanisms producing linear in temperature d.c. resistivity.
BKT quantum phase transitions are commonplace in holographic descriptions of
finite density matter, separating critical and ordered phases. We show that at
a holographic BKT critical point, if the unstable operator is coupled to the
current via irrelevant operators, then a linear contribution to the resistivity
is universally obtained. We also obtain broad power law tails in the optical
conductivity, that shift spectral weight from the Drude peak as well as
interband energy scales. We give a partial realization of this scenario using
an Einstein-Maxwell-pseudoscalar bulk theory. The instability is a vectorial
mode at nonzero wavevector, which is communicated to the homogeneous current
via irrelevant coupling to an ionic lattice.
