How do I get my players to roleplay with each other more?

I tend to find with one group that unless there is an npc or DM pc thrown in there, there is little dialogue. Im trying to get them to talk more in character and find they do that when I initiate it either through getting a DM pc to do something stupid or they talk to an NPC but when I just explain a scene and leave em to it and do nothing with an NPC they rarely engage in, in character conversations. Im trying to not lead them with DM pcs to initiate pointless party banter want the spotlight on the PCs not thier companions.