  Recent studies of the high-Tc superconductor La_(1.6-x)Nd_(0.4)Sr_(x)CuO_(4)
(Nd-LSCO) have found a linear-T in-plane resistivity rho_(ab) and a logarithmic
temperature dependence of the thermopower S / T at a hole doping p = 0.24, and
a Fermi-surface reconstruction just below p = 0.24 [1, 2]. These are typical
signatures of a quantum critical point (QCP). Here we report data on the c-axis
resistivity rho_(c)(T) of Nd-LSCO measured as a function of temperature near
this QCP, in a magnetic field large enough to entirely suppress
superconductivity. Like rho_(ab), rho_(c) shows an upturn at low temperature, a
signature of Fermi surface reconstruction caused by stripe order. Tracking the
height of the upturn as it decreases with doping enables us to pin down the
precise location of the QCP where stripe order ends, at p* = 0.235 +- 0.005. We
propose that the temperature T_(rho) below which the upturn begins marks the
onset of the pseudogap phase, found to be roughly twice as high as the stripe
ordering temperature in this material.
