Extract a part of names before the start of a patern in linux?

I can list all files ls *.nc

 kjkh_lkm_kkkkk_abc_195101-196012.nc
 kjkh_lkm_kkkkk_abc_198101-196012.nc
 LM_lkm_kjjkk_abc_196101-196012.nc
 kjkh_lkm_kjjkk_abc_196101-196012.nc
 SAM_lkm_abc_196101-196012.nc
 kjk_lkm_abc_196101-196012.nc

However, I need to extract the parts before _abc ? if more than one, just ignore

 kjkh_lkm_kkkkk
 LM_lkm_kjjkk
 kjkh_lkm_kjjkk
 SAM_lkm
 kjk_lkm

>Solution :

Here:

ls *.nc|sed -E 's/_abc.*//'|sort|uniq > newfile