Abstract. The spt-function spt(n) was introduced by Andrews as the weighted counting of partitions of n with respect to the number of occurrences of the smallest part. Andrews, Garvan and Liang defined the spt-crank of an S-partition which leads to combinatorial interpretations of the congruences of spt(n) mod 5 and 7. Let N S (m, n) denote the net number of S-partitions of n with spt-crank m. Andrews, Garvan and Liang showed that N S (m, n) is nonnegative for all integers m and positive integers n, and they asked the question of finding a combinatorial interpretation of N S (m, n). In this paper, we introduce the structure of doubly marked partitions and define the spt-crank of a doubly marked partition. We show that N S (m, n) can be interpreted as the number of doubly marked partitions of n with spt-crank m. Moreover, we establish a bijection between marked partitions of n and doubly marked partitions of n. A marked partition is defined by Andrews, Dyson and Rhoades as a partition with exactly one of the smallest parts marked. They consider it a challenge to find a definition of the spt-crank of a marked partition so that the set of marked partitions of 5n + 4 and 7n + 5 can be divided into five and seven equinumerous classes. The definition of spt-crank for doubly marked partitions and the bijection between the marked partitions and doubly marked partitions leads to a solution to the problem of Andrews, Dyson and Rhoades.