If you lump materialism in with physicalism, then Freud certainly had materialist thinking. The TLDR is Feudian theories ground thought in the body. Radical idealism rejects the body exists, and moderate German views of the period claim that the link between mind and body is at best a correlation. Consider Freud's academic training:
Freud entered the University of Vienna at age 17. He had planned to study law, but joined the medical faculty at the university, where his studies included philosophy under Franz Brentano, physiology under Ernst Brücke, and zoology under Darwinist professor Carl Claus.[20] In 1876, Freud spent four weeks at Claus's zoological research station in Trieste, dissecting hundreds of eels in an inconclusive search for their male reproductive organs.[21] In 1877, Freud moved to Ernst Brücke's physiology laboratory where he spent six years comparing the brains of humans and other vertebrates with those of frogs and invertebrates such as crayfish and lampreys. His research work on the biology of nervous tissue proved seminal for the subsequent discovery of the neuron in the 1890s.[22] Freud's research work was interrupted in 1879 by the obligation to undertake a year's compulsory military service.
So, Freud was clearly a scientist in the sense of late-19th century German philosophy and science, arguably one of the world's most active and innovative places for psychological research. Remember, for clinical psychologists today, the two big names in the origins of modern psychology are Freud and Wundt, who opened the world's first research lab and is the considered by most many sources as the father of experimental psychology. Freud and his ideas are controversial today, and he and his doctrines are often seen as pseudoscientific. If you read Why Freud Was Wrong (GB), you'll find it a scathing review of him and his ideas, though his ideas have been tremendously influential and inspired existentialists as well as modern day psychoanalysts.
Philosophically, there were many thinkers during his day who rejected any connection between logical thinking and psychology, a view Kant promulgated in his Introduction to Logic which is part of the German philosophical exploration between the mind and the body which followed in the wake of Kant's Critiques and his transcendental idealism. While Freud wasn't part of the debate on logicism, the reduction of logic to human thought, Freud did promulgate views that grounded human thought in human biology. Consider:
- Freud was a neurologist. As primitive as neurology was then compared to now, neurology is a physical science, and Freud exploited the science in his own views.
- Freud's model of thinking was mechanistic and used the metaphor of physical pressure to describe it's function. Counter to Descartes and rationalism, he believed there were aspects of the mind that were a function of the brain and that were not accessible to introspection. That stands in distinction to the idealism of Berkeley in which the material didn't exist at all. Freud's thinking could be thought to be in the model of Newtonian mechanism, the idea that mathematical Laws of Nature govern everything, including thought. This might be the heart of the physicalist program: reduce everything, including thought to deductive, mathematical laws.
- Freud specifically thought biological instincts shaped thoughts. In particular, Freud was a believer that one's training of bowels (anal retentiveness and expulsiveness) affected one's personality, and that sexual impulses drove other subconscious decision making. It's very materialist to have reductionist theories of mind to body, and to accept mental causation.
- Freud's methodology of therapy was the methodology of medical doctors. To this day, it annoys humanist-centered talk therapists to see fellow psychologists to pathologize their clients' thinking. This practice clearly has roots in Freudian thinking. It's not uncommon to hear psychologists today use the term "present" for instance to describe thoughts and behavior much as infectious disease specialists do. This tendency reached an extreme and created an antipsychiatry backlash in the 60's and 70's and has morphed into positive psychology movement today.
My answer is already way longer than I want, but I'll just repeat at this point. Despite being pseudoscientific by today's standards, in the context of his historical period, Sigmund Freund qua neurologist was very much a physicalist who sought to reduce explanations of the mind to those of the body, and show how the mind supervened on the brain. Such thinking was dominant until behaviorism displaced that sort of thinking rejecting the mental entirely in its radical form, and came back in vogue to some extent among the cognitive psychology paradigm shift when operationalism and behaviorism fell out of favor.
