Global geomagnetic data are inverted for detecting a high-conductivity layer at depths of 1500-2000. km to test the hypothesis of a magnesiowustite phase transition in the lower mantle. We present the results of processing of both synthetic and global data-average monthly values of the geomagnetic field from 1920 to 2009. The inverted global data are consistent with the possible existence of a high-conductivity layer at great depths in the lower mantle
