This work summarizes the studies in Condensed Matter Physics which were directed by Profs. Hermann Suderow and Sebastián Vieira at the Low Temperature Laboratory of Universidad Autónoma de Madrid. It includes a description of the experimental set up and the subsequent experiments. The former consists of a scanning tunneling microscope installed in the coolest part of a dilution refrigerator able to operate at millikelvin temperatures and high magnetic fields. In addition, a method to apply electrical current through superconducting samples was developed. The experiments performed using this system include superconducting vortex dynamics under current flow and the exploration of new phases in different heavy fermion compounds.