The fields of sociology and psychoanalysis are already interconnected as it is. Sociology studies mainly actions, processes, phenomena, and facts related to human society. The term was put forth by Auguste Comte in 1847, approximately, to replace the term put forth by Saint-Simon in 1813, of "social physiology". In Durkheim's view, it is a "science" because there are methodologies in place that are dedicated to analyze how things occur, and how people influence their environment (and vice versa). It is also a science because it has expected and predictable outcomes that come out from interaction with others, or what Simmer would call the "social forms". Sociology is the collective study of people, groups, and dynamics
On the other hand, psychoanalysis is the in-depth study of the internal, mental processes that affect the emotional state of the individual, and the behaviors associated with it. It is also a science in the way that methodologies such as psychotherapy, Gestalt, and Person-Center approach (for example) are put in place. That is connected to sociology in that both, the individual and the collective behavior of groups are analyzed, and even predicted.
Just like with sociology, the term "sociopsychoanalysis" has not yet been officially embraced in modern social studies, but the purpose of it as a field is to connect the inner psychology under Freud's anthropological parameters to social phenomena. Hence, the discipline wants to literally spell out that there is a connection between the rogue nature of human psychology and the phenomenology that takes place everyday: to what point can that inner psyche affect society collectively?
The advent of the discipline can be traced back to Freud himself, who consistently argued that the unconscious is what drives human behavior, or at least the majority of it; that our choices, our personalities, likes, dislikes, hopes, and fears are all interconnected to the secret ideas, hidden emotions, and repressed memories that lurk inside our brains. If this is, indeed, a fact (and the unconscious does play a pivotal part in behavior), then we can ascertain that the unconscious of all people, collectively, creates the social phenomena that we call "reality". This includes the mental evolution of us as a civilization, the onset of wars, the creation of philosophical constructs, and even the establishment of financial models. How does the unconscious of each individual, and the behavior that arises as a result of it, affect major changes in society? That is ultimately what this discipline aims to explain.
For additional information refer to:
Freud, Sigmund. (1907b). Obsessive actions and religious practices. SE, 9: 115-127.