ab-plane resistivity and possible charge stripe ordering in strongly underdoped La${}_{2-x}$Sr${}_x$CuO${}_4$ single crystals

We have measured the ab-plane resistivity of La${}_{2-x}$Sr${}_x$CuO${}_4$ single crystals with small Sr content (x=0.052 $÷$ 0.075) between 4.2 and 300 K by using the AC Van der Pauw technique. As recently suggested by Ichikawa et al., the deviation from the linearity of the ${\rho }_{\mathrm{a}\mathrm{b}}(T)$ curve starting at a temperature T${}_{\mathrm{c}\mathrm{h}}$ can be interpreted as due to a progressive slowing down of the fluctuations of pre-formed charge stripes. An electronic transition of the stripes to a more ordered phase could instead be responsible for some very sharp anomalies present in the ${\rho }_{\mathrm{a}\mathrm{b}}(T)$ of superconducting samples just above $T_{\mathrm{c}}$.