Persistent X-ray photoconductivity and percolation of metallic clusters in charge-ordered manganitesD. Casa, V. Kiryukhin, O. A. Saleh, B. Keimer, J. P. Hill, Y. Tomioka and Y. TokuraEurophys. Lett., 47 1 (1999) 90-96DOI: https://doi.org/10.1209/epl/i1999-00356-y