Context :

Aims : Polarization measurements of the Galactic plane at \lambda 6 cm probe the interstellar medium ( ISM ) to larger distances compared to measurements at longer wavelengths , hence enable us to investigate properties of the Galactic magnetic fields and electron density .

Methods : We are conducting a new \lambda 6 cm continuum and polarization survey of the Galactic plane covering 10 \degr \leq l \leq 230 \degr and |b| \leq 5 \degr .
Missing large-scale structures in the U and Q maps are restored based on extrapolated polarization K-band maps from the WMAP satellite .
The \lambda 6 cm data are analyzed together with maps at other bands .

Results : We discuss some results for the first survey region , 7 \degr \times 10 \degr in size , centered at ( l,b ) = ( 125 \aas@@fstack { \circ } 5 , 0 \degr ) .
Two new passive Faraday screens , G125.6 - 1.8 and G124.9 + 0.1 , were detected .
They cause significant rotation of background polarization angles but little depolarization .
G124.9 + 0.1 was identified as a new faint HII region at a distance of 2.8 kpc .
G125.6 - 1.8 , with a size of about 46 pc , has neither correspondence in enhanced H \alpha emission nor a counterpart in total intensity .
A model combining foreground and background polarization modulated by the Faraday screen was developed .
Using this model , we estimated the strength of the ordered magnetic field along the line of sight to be 3.9 \mu G for G124.9 + 0.1 , and exceeding 6.4 \mu G for G125.6 - 1.8 .
We obtained an estimate of 2.5 and 6.3 mK kpc ^ { -1 } for the average polarized and total synchrotron emissivity towards G124.9 + 0.1 .
The synchrotron emission beyond the Perseus arm is quite weak .
A spectral curvature previously reported for SNR G126.2 + 1.6 is ruled out by our new data , which prove a straight spectrum .

Conclusions : The new \lambda 6 cm survey will play an important role in improving the understanding of the properties of the magneto-ionic ISM .
The magnetic fields in HII regions can be measured .
Faraday screens with very low electron densities but large rotation measures were detected indicating strong and regular magnetic fields in the ISM .
Information about the local synchrotron emissivity can be obtained .