Parallax ratio (bottom) and proper motion differences (upper two panels) as a function of the maximum RUWE in a CPPM pair. Only stars with a parallax precision better than 20% were considered in our search for CPPM stars around 84 and 154 old and new Ap stars (see text). Open and filled symbols show the candidates after our initial and final search criteria, respectively. The dashed lines mark our final CPPM criteria, and the vertical solid line shows the recommended limit of the RUWE for astrometrically well-behaved objects.