What is the structure in front of the entrance to Menkaure's pyramid?

So far, I have only found short notices or massively outdated material.

Peter Jánosi, Bemerkungen zu den Nordkapellen des Alten Reiches 1995 has a footnote (p. 150) that says

Das bisher nicht näher identifizierte "Nordgebäude" bei der Mykerinospyramide ist nicht als Nordkapelle anzusehen und dürfte aus späterer Zeit stammen, Maragioglio/Rinaldi, op.cit. VI, Addenda 1970, 3f.; A. Fakhry, The Pyramids. 1961, 258; R. Stadelmann, Die ägyptischen Pyramiden. Vom Ziegelbau zum Weltwunder, 1992, 147, Taf. 54.

The so far unidentified "north building" near the Mykerino pyramid is not to be regarded as a north chapel and probably dates from a later period.

Maragioglio/Rinaldi is online available only in its 1967 edition which does not contain the 1970 Addenda. On p. 48, the existence of a north chapel is placed in doubt:

The base of the northern face of the pyramid is still largely cluttered with rubble which, towards the centre, reaches a considerable height. There is therefore nothing to suggest whether or not there was a place of worship to the north of the pyramid opposite the entrance.

Although, on p. 78, another structure (called a "pit") on the north side is mentioned, which was noticed already in the 19th century.

Vyse (Operations etc. cit., I, p. 6; II, p. 15) noted to the north of the pyramid, in line with the large breaches made in the nucleus, a rectangular pit of uncertain date with sides 20-30 feet long (about 6-9 m.).

The excavation was faced to west and south with stone masonry and its bottom seems to have been paved. According to Vyse the pit was dug in the foundation terracing.

If the surrounding courtyard had the same width to the north as it did to the east (about 10 m.) this pit was located outside the inner boundary wall.

The ruin naturally requires systematic excavation before it can be determined whether or not it formed part of the pyramid of Mycerinus and, if so, what its function was.

Vyse 1840 itself had the following to say, which is not really helpfull from today's perspective.

[vol. I, p. 6f] Opposite the centre, and at some little distance from the base of the Pyramid, a pit about 20 or 30 feet square had been excavated in the rubbish, the sides of which had been supported by a revetment of large stones. Several blocks had been forced from a paveinent at the bottom of this pit, it would seem in search of an entrance into the Pyramid, and many others yet remained there, similar to those afterwards uncovered to the eastward; but there was no appearance that the Pyramid had ever been opened.

[vol. II, p. 15f] In consequence of some remarks, that Mr. Perring and Mr. Mash had made during their survey, I examined very particularly a square pit at the northern front of this building. It appeared to have been made in search of an entrance, and was reveted on the western side, and on that next the pyramid, to keep up the surrounding rubbish, that extended along the front of the building, and contained enormous masses of calcareous stone and of granite, and other fragments chiefly produced by two large chasms, which had been made one above the other in the face of the pyramid, and were said by M. Denon to have been the works of the Mamelucs...At first, the bottom of the pit appeared to be rock, but upon closer examination it was found to consist of large stones, the upper tier of which had been removed. It was, in fact, a continuation of the pavement subsequently discovered to the eastward... Gunpowder appeared to have been made use of in the removal of the stones at the bottom of the pit...

Fakhry 1961 is only available on loan.

Stadelmann 1992 speculates the building is one of the numerous burials from the 26th dynasty (664–525 BC) on the Gizeh plateau:

Der umgebende Pyramidenhof ist nur an der Ostseite ausgegraben. An der Nordseite ist unterhalb des Einganges in jüngster Zeit ein Bauwerk mit drei Kapellen nach Norden und einem Hof freigelegt worden, das aber wohl eher ein saitischer Grabbau als die Nordkapelle sein wird.

The surrounding pyramid courtyard has only been excavated on the east side. On the north side, below the entrance, a structure with three chapels facing north and a courtyard has recently been uncovered, but this is more likely to be a Saite burial structure than the north chapel.

Wafaa el-Saadek: Twenty-Sixth Dynasty Necropolis at Gizeh, 1984 makes no mention of this particular building. Abdel-Aziz Sadeh 1974, describing the 1971/72 excavation campaign says "the northern front of the Pyramid is left to be dealt with by the Egyptian Department of Antiquities". In an aerial photo from 1983 the north side is cleaned up and the structure can be seen. Equally, the topographical map prepared by Mark Lehner in the 1980s has it. This seems to point to excavation works done during the 1970s or 80s, but I have not been able to identify who and when exactly.