High symmetry molecules fit into crystal lattices especially well (higher mp), but are volatile for having fewer van der Waals interactions (lower bp)

Pentane mp -130 C, bp 36.1 C <BR>
isopentane,  mp -160 C , bp 27.2 C <BR>
neopentane, mp -18 C, bp 9.5 C

octane, mp -57 C, bp 125 C <BR>
2-methylheptane, mp -110 C, bp 117 C <BR>
2,2,4-trimethylpentane, mp -107 C, bp 99 C <BR>
2,2,3,3-tetramethylbutane, mp 101 C, bp 107 C <BR>
cubane, mp 131 C, bp 133 C (sublimes at room temp)

decane,  mp -30 C, bp 174 C <BR>
isodecane, mp -75 C, bp 167 C <BR>
adamantane mp  270 C, sublimes