Tosefta do Daniela 8:29

The priestly portion of a chaver and the priestly portion of an am ha'aretz that got mixed up together, we compel the am ha'aretz to sell his portion. A Kohen (lit., "Jewish Priest") [can] share [the priestly portion] with a Samaritan Priest within Samaritan territory, because he is like one who delivers from his hand (Dan. 8:4) [per Lieberman, otherwise the entire priestly portion would go to the Samaritan, so in essence by taking a portion, the Jew is "delivering" part of the Terumah from the hand of the Samaritan]. However, this is not done in the Land [of Israel], lest [the Samaritans] have presumptions on (i.e., believe themselves entitled to the privileges of) the priesthood [in the Land of Israel]. But in the Land of Israel, in a place that they know him (i.e., the Samaritan Priest (perhaps implying that the population is diverse in that locale)), it is permitted to share with him.