Does a split card in the graveyard count as both halves for cards like Snapcaster Mage targeting one half?

A split card in any zone other than the stack has the combined characteristics of both halves at once (CR 709.4). This means a card like Fire // Ice in the graveyard is simultaneously a red instant that deals damage AND a blue instant that draws a card, with a combined converted mana cost of 4 (2+2) for most purposes.

When a spell or ability asks you to target a card in the graveyard — such as Snapcaster Mage's triggered ability granting flashback — the split card as a whole is the legal target. The split card is one card, so Snapcaster Mage targets that one card (CR 709.1).

However, when you actually cast the split card using the granted flashback ability, you choose to cast only one half of it (CR 709.4a). You cannot cast both halves simultaneously unless an ability like Fuse specifically allows it (CR 709.4b, 702.101). So Snapcaster Mage enables you to flash back either Fire OR Ice, not both.

Concrete example: You have Fire // Ice in your graveyard. Snapcaster Mage enters and gives it flashback. You target Fire // Ice — that's one legal target. When you cast it with flashback, you choose to cast only Ice (tap a permanent, draw a card). Fire is not cast and the whole card is then exiled.

Key citations: CR 709.1 (split cards are single cards), CR 709.4 (characteristics in zones other than stack), CR 702.101 (fuse keyword for casting both halves).