Off the top of my head I can think of the interlude between solos in Moonchild (E - B - Bb), of the Wasting Love arpeggio (the second chord is D11/C which includes a C - F# tritone), of Sign of the Cross in the instrumental breakdown before the fast part and of Speed of Light. The solo section in Paschendale includes a tritone modulation: Dave's solo is in E minor, Adrian's in C# minor, Bruce's verse ("Blood is falling like the rain") in G# minor and Janick's solo is in D minor, a tritone jump.
Also in Alexander the Great (break after Adrian's 7/8 solo), the pre-chorus of Powerslave (Dave's part goes E - C - Bb/B/Bb) are other examples (and in the lick at the end of the main riff too, it uses both E and Bb).
Oh, and in The Talisman's main riff too, IIRC the second repetition ends with F - E(b5). Not mentioning Janick's solo.
Adrian also used tritones in his second solo in Seventh Son of a Seventh Son (and the riff under the solos uses tritones too).
But given IM's melodic style is not that easy to throw dissonances around. Metallica's more aggressive riffwriting (especially in the Burton-era) opened to more possibilities.