Normal map problem

Hi guys,as you can see in the image below I got an head unwrapped but with a seam on the chin & the seam is extremely visible on the normal map (check the rough bake,last image).
I have attempt the bake with a single smoothing group & with 1 smoothing group for each uvshell,but the resoult is always a visible seam,so my question is,I am missing something or actually there is no a way to get rid of that without modifying my unwrap??