Found:

infix

MORPHOLOGY: an affix which is placed inside another morpheme. EXAMPLE: Tagalog, a language spoken at the Philippines, has a number of infixes. From the monomorphemic root sulat 'writing' the derived verb sumulat 'to write' is formed by infixing -um- after the initial consonant. The existence of infixes is not uncontroversial. Broselow & McCarthy (1983) and McCarthy (1986) argue that infixation is just a special kind of prefixation or suffixation.

LIT.	Broselow, J. & J. McCarthy (1983) McCarthy, J. (1986)