  Polar metals with ferroelectric-like displacements in metals have been
achieved recently, half century later than Anderson and Blount's prediction.
However, the genuine ferroelectricity with electrical dipolar switching has not
yet been attained experimentally in the conducting materials, especially the
ones possessing magnetic responses. Here we report the coexistence of
ferroelectricity and magnetoresistance (MR) in the metallic PbNb0.12Ti0.88O3
(PNTO) thin films. We found that the conducting and magnetic responses of PNTO
films are highly asymmetric. Negative MR up to 50% is observed under an
in-plane magnetic field; the MR switches to positive with the magnetic field
applied parallel to the surface normal. Such unique behavior is attributed to
the moving electron caused effective magnetic field which couples with the
spins of electrons, which form a dynamic multiferroic state in the metallic
PNTO. These findings break a path to multiferroic metal and offer a great
potential to the multi-functional devices.
