Why is there no official character song for Homura and Mami? Madoka has a character song titled "See You Tomorrow" (またあした, Mata Ashita) while Sayaka and Kyoko have a duet song titled "And I'm Home".

I just found out that Homura and Mami don't have a character song (from this Puella Magi wiki page) like Madoka, Sayaka, and Kyoko do. Are there any character songs for Homura and Mami? If there aren't, why didn't they make one for them?

Added to clarify, by character song I mean


  A song whose vocals are credited to the character or characters singing the song. 


as per this question What is a “character song”?
I'm not sure precisely how a character's "official" song is defined, but a "Credens Justitiam" is, in my experience, often associated with Mami. Here's one source that sites this as the case. Further, for a more speculative approach, this is the song that plays during several of the scenes involving Mami, and, likewise, 


   no longer seems to play in the anime after Mami dies (if memory serves me correctly).


Thus it would make sense that this is identified as her theme song.

As for Homura's song, the same source I listed earlier states that Homura's theme song is "Puella in Somnio" ("The Girl in the Dream"). Google searching "homura's theme" also will return several YouTube videos all of this song. As before, I believe this song is played most often (if not exclusively) in scenes directly involving or featuring Homura.