High-resolution spectroscopy of ( catalog U Gem ) was obtained during quiescence .
We did not find a hot spot or gas stream around the outer boundaries of the accretion disk .
Instead , we detected a strong narrow emission near the location of the secondary star .
We measured the radial velocity curve from the wings of the double-peaked H \alpha emission line , and obtained a semi-amplitude value that is in excellent agreement with the obtained from observations in the ultraviolet spectral region by Sion et al . ( 28 ) .
We present also a new method to obtain K _ { 2 } , which enhances the detection of absorption or emission features arising in the late-type companion .
Our results are compared with published values derived from the near-infrared NaI line doublet .
From a comparison of the TiO band with those of late type M stars , we find that a best fit is obtained for a M6 V star , contributing 5 percent of the total light at that spectral region .
Assuming that the radial velocity semi-amplitudes reflect accurately the motion of the binary components , then from our results : K _ { em } = 107 \pm 2 km s ^ { -1 } ; K _ { abs } = 310 \pm 5 km s ^ { -1 } , and using the inclination angle given by Zhang & Robinson ( 42 ) ; i = 69.7 ^ { \circ } \pm 0.7 , the system parameters become : M _ { WD } = 1.20 \pm 0.05 M _ { \odot } ; M _ { RD } = 0.42 \pm 0.04 M _ { \odot } ; and a = 1.55 \pm 0.02 R _ { \odot } .
Based on the separation of the double emission peaks , we calculate an outer disk radius of R _ { out } / a \sim 0.61 , close to the distance of the inner Lagrangian point L _ { 1 } / a \sim 0.63 .
Therefore we suggest that , at the time of observations , the accretion disk was filling the Roche-Lobe of the primary , and that the matter leaving the L _ { 1 } point was colliding with the disc directly , producing the hot spot at this location .