Transport in crystalline ${\mathrm{La}}_2$${\mathrm{CuO}}_{4+\mathrm{\delta }}$: Enormous anomalies at $T_N$ for small hole doping

The anisotropic electrical resistivity ρ and thermoelectric power S have been determined on single crystals of ${\mathrm{La}}_2$ ${\mathrm{CuO}}_{4+\mathrm{\delta }}$ in which the hole doping δ has been varied by controlled anneals. An enormous decrease and hysteresis in both ρ and S occur at the Néel temperature $T_N$ for small δ, suggesting strong coupling between magnetic order and transport. Possible origins of these transport anomalies are discussed.