There is no conclusive internal evidence but there are plenty of pointers that lend themselves to the conclusion that Peter is in some way the source, for example this list from here:
Peter is the first and last named disciple in Mark (1:16; 16:7).
Peter is mentioned more than any other disciple in Mark.
Peter appears in some of the most important scenes in Mark: the calling of the first disciples (1:16-20), the confession of Jesus as Messiah (8:27-30), the transfiguration (9:2-8), the prayer in Gethsemane (14:32-42), and in the concluding scene alluding to future appearances of Jesus (16:7).
Of the four gospels, Mark has the highest percentage of references to boats, the Sea of Galilee, and fishing. Peter apparently was a fisherman who worked on the Sea of Galilee (1:16).
There is the curious story of the healing of Peter’s mother-in-law (1:29-31), which seems to include personal details related to Peter.
Of these I give the last the most weight.
Also, only Peter, James and John were present at the transfiguration, so it is likely that one of them passed on the account to Mark:
2And after six days Jesus took with him Peter and James and John, and led them up a high mountain by themselves. And he was transfigured before them, 3and his clothes became radiant, intensely white, as no one on earth could bleach them. 4And there appeared to them Elijah with Moses, and they were talking with Jesus. 5And Peter said to Jesus, “Rabbi, it is good that we are here. Let us make three tents, one for you and one for Moses and one for Elijah.” 6For he did not know what to say, for they were terrified. 7And a cloud overshadowed them, and a voice came out of the cloud, “This is my beloved Son; listen to him.” 8And suddenly, looking around, they no longer saw anyone with them but Jesus only. Mark 9, ESV
This is very similar to Peter's account in 2 Peter:
17For when he received honor and glory from God the Father, and the voice was borne to him by the Majestic Glory, “This is my beloved Son, with whom I am well pleased,” 18we ourselves heard this very voice borne from heaven, for we were with him on the holy mountain. 2 Peter 1, ESV
So, Is there also material internal to Mark's gospel to suggest that it reflects the memoirs of Peter?
Yes, but the key word here is "suggest". There is no direct proof but also no strong reason to suggest otherwise, which is important too.