let $g $ be a finite group and let $gamma(g)$ be the prime graph of g. assume $2 < q = p^{alpha} < 100$. we determine finite groups g such that $gamma(g) = gamma(u_3(q))$ and prove that if $q neq 3, 5, 9, 17$, then $u_3(q)$ is quasirecognizable by prime graph, i.e. if $g$ is a finite group with the same prime graph as the finite simple group $u_3(q)$, then $g$ has a un...