  A new formation scenario for TiC and Fe,Ni-metal inclusions in presolar
graphite grains of supernova origin is described. The mineralogy and chemistry
require condensation of (Fe,Ni)-titanides from Fe, Ni, and Ti-rich gaseous
ejecta, subsequent carburization to make TiC and metal, and encapsulation into
graphite. Titanides only condense if Si is depleted relative to heavier mass
elements, which requires alpha-rich freeze-out and a deep mass-cut for the
supernova ejecta. This Si-poor core material must remain unmixed with other
supernova zones until the titanides condensed. This can be accomplished by
transport of core ejecta in bipolar jets through the major expanding supernova
zone ejecta. If the jets stall in regions dominated by C-rich ejecta such as
C-He zone where graphite condenses, thermochemically favored in situ
carburization of the titanides - either before or during encapsulation into
condensing graphite - leads to a TiC and metal composite. This scenario agrees
with theoretical models and observations of asymmetric core collapse in
supernovae that are associated with bipolar jets loaded with iron-peak
elements.
